METHODS  OF  GAS  ANALYSIS 


METHODS  OF  GAS  ANALYSIS 


BY 


DR.    WALTHER  HEMPEL 

ti 

PROFESSOR  OP  CHEMISTRY  IN  THE  DRESDEN   TBCHN1SCHX 
HOCHSCHULE 


TRANSLATED  FROM  THE  THIRD  GERMAN  EDITION 
AND  CONSIDERABLY  ENLARGED 

BY 

L.    M.    DENNIS 

PROFESSOR  OF  ANALYTICAL  AND    INORGANIC  CHEMISTRY 
IN  CORNELL  UNIVERSITY 


THE    MACMILLAN   COMPANY 

LONDON :  MACMILLAN  &  CO.,  LTD. 

1912 

All  right*  reserved 


Engineering 
Lib1 


COPYRIGHT,  1902, 
BY  THE  MACMILLAN  COMPANY. 


Set  up  and  electrotyped.     Published  March,  1902. 
Reprinted  October,  1906  ;  June,  1910;  September,  1911 
September,  1912. 


Nortoooto 

J.  S.  Gushing  &  Co.  —  Berwick  &  Smith  Co. 
Norwood,  Mass.,  U.S.A. 


PREFACE   TO   THE   SECOND   GERMAN 
EDITION 

IN  publishing  my  "  New  Methods  for  the  Analysis 
of  Gases,"  it  was  not  my  intention  to  write  a  manual 
of  gas  analysis,  but  merely  to  describe  my  own  re- 
searches and  the  construction  of  apparatus.  My 
present  plan,  however,  after  ten  years'  experience 
and  the  most  varied  work  with  gases  and  their 
analysis,  is  to  describe  all  of  the  operations  which 
are  involved  in  the  analysis  of  gases  with  my  appa- 
ratus. I  have  thought  to  give  the  book  especial 
value  by  limiting  myself  to  the  description  of  those 
methods  which,  in  my  opinion,  are  at  the  present 
time  the  most  practical.  I  have  not  endeavoured  to 
give  a  complete  description  of  all  known  methods, 
because  the  book  would  then  become  too  bulky  to 
be  used  as  the  laboratory  guide  which  it  is  intended 
to  be. 

The  apparatus  devised  by  Pettersson  has  been 
described,  because  a  wholly  new  principle  in  the 
measurement  of  gases  is  there  brought  into  use.  In 
the  following  pages  I  hope  to  give  a  guide  to  gas 
analysis  by  the  help  of  which  the  various  examina- 
tions, even  the  most  difficult,  can  be  carried  out. 

WALTHER  HEMPEL. 
DRESDEN, 
December,  1889. 

V 

268700 


PREFACE   TO   THE  TRANSLATION   OF 
THE   SECOND   GERMAN   EDITION 

THE  rapidly  growing  recognition  of  the  impor- 
tance of  gas  analysis  in  the  field  of  industrial  as 
well  as  of  pure  chemistry,  has  made  it  seem  probable 
that  a  translation  of  the  latest  work  of  so  eminent 
an  investigator  in  this  line  as  Professor  Hempel 
might  prove  acceptable  to  English-reading  chemists. 
While  preparing  this  English  edition,  the  Translator 
was  so  fortunate  as  to  enjoy  throughout  the  progress 
of  the  work  the  personal  cooperation  of  the  author, 
and  the  changes  that  have  been  made  were  either 
suggested  by  Professor  Hempel  himself,  or  inserted 
with  his  approval.  The  chapter  upon  the  determi- 
nation of  the  heating-power  of  fuel  has  been  largely 
rewritten,  and  new  cuts  of  the  latest  forms  of  appa- 
ratus have  been  introduced  in  the  place  of  those  in 
the  German  edition.  The  chapter  upon  the  analysis 
of  illuminating  gas  has  also  been  somewhat  changed, 
and  a  new  method  for  the  determination  of  the 
hydrocarbon  vapours  inserted.  The  other  and  less 
important  alterations  have  been  made  in  the  desire 
to  incorporate  so  far  as  possible  the  researches  that 
have  appeared  since  the  publication  of  the  German 
edition. 

L.  M.  DENNIS. 

ITHACA,  NEW  YORK, 
November,  1891. 


PREFACE   TO  THE  THIRD   GERMAN 
EDITION 

MANY  important  investigations  in  the  field  of  gas 
analysis  have  been  published  in  the  interval  that  has 
elapsed  since  the  appearance  of  the  second  edition 
of  this  work,  and  it  is  with  the  idea  of  bringing 
together  these  and  his  own  experimental  researches 
that  the  author  has  been  led  to  prepare  this  third 
edition. 

The  division  into  technical  and  exact  gas  analysis 
has  been  abandoned  because,  on  the  one  hand,  appa- 
ratus originally  intended  for  technical  purposes  may 
advantageously  be  employed  for  many  purely  scien- 
tific investigations,  and,  on  the  other  hand,  technical 
analyses  must  often  satisfy  the  most  exacting  de- 
mands as  to  accuracy. 

DR.  WALTHER  HEMPEL. 

DRESDEN, 
November,  1899. 


vfl 


PREFACE   TO   THE   TRANSLATION   OF 
THE   THIRD   GERMAN   EDITION 

IN  this  translation  of  the  third  German  edition 
of  Professor  Hempel's  "  Methods  of  Gas  Analysis," 
the  work  has  been  thoroughly  revised  by  both  the 
author  and  the  Translator,  and  has  been  changed  to 
such  an  extent  that  this  translation  may  indeed  be 
regarded  as  a  fourth  edition  of  the  book. 

The  determination  of  atmospheric  oxygen  by 
Kreusler's  method  has  been  omitted.  The  additions 
comprise  several  new  methods  of  collecting  and 
keeping  gas  samples ;  determinations  with  the  Ho- 
nigmann,  Bunte,  and  Orsat  apparatus ;  the  new 
Hempel  methods  for  exact  gas  analysis ;  new  meth- 
ods for  the  determination  of  combustible  gases ;  the 
separation  of  argon  from  the  atmosphere  ;  improved 
methods  for  the  determination  of  carbon  monoxide 
in  gas  mixtures ;  the  analysis  of  acetylene  gas ;  the 
examination  of  gases  produced  by  living  bacteria ; 
the  simultaneous  determination  of  fluorine  and  car- 
bon dioxide ;  the  determination  of  the  heating  power 
of  gases  ;  sulphur  in  organic  substances ;  the  gas 
lantern ;  the  volumetric  determination  of  carbon  in 

ix 


X  PREFACE  TO  TRANSLATION 

iron ;  the  analysis  of  gases  evolved  in  the  electrol- 
ysis of  chlorides  and  in  the  manufacture  of  bleach- 
ing powder,  together  with  many  minor  changes  and 
additions  throughout  the  book. 

L.  M.  DENNIS. 
ITHACA,  NEW  YORK, 
March,  1902. 


CONTENTS 


PART  I 

GENERAL  METHODS 
CHAPTER  I 

PAGE 

THE  COLLECTING  AND  KEEPING  OF  GASES     ....  3 

Collecting  Gases  from  Furnaces        .....  3 

Collecting  Samples  of  Mine  Gas 4 

Collecting  Samples  of  Air 6 

Collecting  Gases  from  Springs 8 

Extracting  the  Absorbed  Gases  from  Liquids  ...  10 
Collecting  Gases  from  Sealed  Tubes          .        .        .        .15 

Extracting  Gases  from  Minerals       .....  16 

Sampling  of  Gases  from  Furnaces 22 

Aspirator 25 

Gas  Holders 26 

CHAPTER  II 

GENERAL    REMARKS    UPON   THE    ANALYSIS    AND    MEASURE- 
MENT OF  GASES 32 

CHAPTER  III 

APPARATUS  FOR  GAS  ANALYSIS  WITH  WATER  AS  THE  CON- 
FINING LIQUID        .......  34 

A.     Gas  Burettes 34 

1.  The  Simple  Gas  Burette 34 

Manipulation  of  the  Gas  Burette       ...  36 

2.  The  Modified  Winkler  Gas  Burette  ...  39 

3.  The  Honigmann  Gas  Burette     .        .         .         .41 

4.  The  Bunte  Gas  Burette 42 

xi 


xii  CONTENTS 

PAGE 

B.     Absorption  Pipettes 47 

1.  The  Simple  Absorption  Pipette          ...  48 

2.  The  Simple  Absorption  Pipette  for  Solid  and 

Liquid  Reagents     ......  49 

3.  The  Double  Absorption  Pipette         ...  50 

4.  The  Double  Absorption  Pipette  for  Solid  and 

Liquid  Reagents 51 

Manipulation  of  the  Absorption  Pipettes  .        .  53 

CHAPTER   IV 

APPARATUS   FOR  EXACT   GAS  ANALYSIS  WITH   MERCURY  AS 

THE  CONFINING  LIQUID          .....  59 

General  Remarks 59 

A.  Apparatus  with  Rubber  Connections  and  Glass 

Stopcocks 59 

I.     Gas  Burettes  with  Correction  for  Variations 

in  Temperature  and  Barometric  Pressure  .  59 

II.     The  Absorption  Pipettes        ....  67 

1.  The  Simple  Mercury  Absorption  Pipette  67 

2.  The  Simple  Mercury  Absorption  Pipette 

for  Solid  and  Liquid  Reagents   .         .  68 

3.  The  Mercury  Absorption  Pipette  with 

Absorption  Bulb         .        .         .         .68 
III.     Gas  Evolution  Apparatus      .        .        .        .71 

B.  Apparatus  for  Exact  Gas  Analysis  without  Rubber 

Connections  or  Stopcocks         ....  76 

Hempel's  Apparatus  for  Exact  Gas  Analysis          .  79 

The  Measuring  Bulb 81 

The  Gas  Pipettes 84 

Method  of  filling  the  Gas  Pipettes  ....  86 

Gas  Pipettes  for  Solid  Absorbents  ....  88 

The  Explosion  Pipette 89 

The  Absorption  Pipette 89 

The  Correction  Tube 94 

CHAPTER  V 

ARRANGEMENT  AND  FITTINGS  OF  THE  LABORATORY       .         .  97 


CONTENTS  xiii 
CHAPTER  VI 

PAGE 

PURIFICATION  OF  MERCUUY    .                  99 

Distillation  in  Vacuum      .......  99 

Purification  by  Nitric  Acid       .        .         .         .        .         .  102 

Purification  by  Air 103 

Purification  by  Concentrated  Sulphuric  Acid  and  Mercu- 

rous  Sulphate 103 

Remarks  upon  the  Making  of  Apparatus  ....  105 

CHAPTER  VII 

ANALYSIS  WITH  THE  USE  OF  ORDINARY  ABSORPTION  APPA- 
RATUS         .........  106 

Remarks  upon  the  Determination  of  very  Small  Quanti- 
ties of  Gas 106 

Pettenkofer's  Absorption  Tube 108 

Winkler's  Absorption  Tube 108 

Peligot  Tube  with  Hempel  Tube 109 

Winkler's  Absorption  Cylinder 109 

Reiset's  Absorption  Apparatus 110 

Simple  Apparatus  for  measuring  Gases         .        .        .112 


PAKT   II 

SPECIAL  METHODS 
CHAPTER  I 

GENERAL  REMARKS  UPON  ABSORPTION  ANALYSES  WITH  THE 

APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS  .  .115 
Accuracy  of  Analyses  made  over  Water  and  over  Mercury  115 
Running  down  of  Confining  Liquids  ....  116 

CHAPTER  II 
CONCERNING  THE  SOLUBILITY  OF  GASES  IN  THE  ABSORBENTS     119 


xiv  CONTENTS 

CHAPTER   III 

PAGE 

CONCERNING  THE  COMBUSTION  OF  GASES        ....  122 

Calculation  of  Results  of  Combustion  Analyses       .        .  122 

The  Explosion  Pipette  for  Technical  Gas  Analysis  .        .  130 

The  Hydrogen  Pipette  for  Technical  Gas  Analysis  .        .  131 

The  Explosion  Pipette  for  Exact  Gas  Analysis         .        .  132 

The  Hydrogen  Pipette  for  Exact  Gas  Analysis         .        .  133 

The  Oxyhydrogen  Gas  Generator 134 

The  Dip  Battery 135 

The  Induction  Coil  . 137 

Combustion  with  an  Electrically  Heated  Platinum  Spiral  138 
Winkler-Dennis  Combustion  Pipette  .  .  .  .138 
Combustion  with  a  Platinum  Capillary  Tube  .  .  .140 

CHAPTER  IV 

PARTICULARS    CONCERNING    THE    DETERMINATIONS    OP    THE 

VARIOUS  GASES          .......  144 

Determination  of  the  "  Analytical  Absorbing  Power  "     .  144 

Oxygen 145 

Ozone 161 

Nitrogen 164 

Gases  of  the  Argon  Group 168 

Separation  of  Argon  from  Atmospheric  Air     .        .        .170 

Hydrogen 175 

Nitrous  Oxide 195 

Nitric  Oxide 197 

Nitrogen  Trioxide 198 

Nitrogen  Tetroxide 199 

Ammonia 199 

Methyl-Amine 200 

Carbon  Dioxide 201 

Carbon  Monoxide 202 

Methane 227 

Ethylene 228 

Acetylene 231 

Cyanogen 233 

Hydrocyanic  Acid 234 


CONTENTS  XV 

PAGE 

Hydrogen  Sulphide 235 

Sulphur  Dioxide 239 

Carbon  Oxysulphide          .......  241 

Chlorine    .         . 244 

Hydrochloric  Acid 246 

Silicon  Tetrafluoride 248 

Phosphine 249 

Arsine 250 

Stibine                                                                                  ,  251 


PART   III 

PRACTICAL  APPLICATIONS  OF  GAS  ANALYSIS 
CHAPTER  I 

COMBUSTION  GASES  —  FURNACE  GASES   .  255 

Sampling  of  Furnace  Gases 256 

The  Orsat  Apparatus         .        .        .        .        .        .        .257 

Gas  Balance  of  Arndt 262 

CHAPTER  H 

ILLUMINATING  GAS  .        . 263 

Water  Gas,  Generator  Gas,  Blast-furnace  Gases,  Coke- 
furnace  Gases        .......    263 

1.  The  Measurement  of  the  Illuminating  Power  .         .     264 

2.  The  Determination  of  the  Specific  Gravity  by  Bun- 

sen's  Method 268 

The  Determination  of  the  Specific  Gravity  by  Schil- 
ling's Method 271 

Gas  Balance  of  Lux 272 

3.  The  Determination  of  Tar,  etc 273 

The  Determination  of  Hydrocarbon  Vapours  by 

Bunsen's  Method 277 

The   Determination  of   Hydrocarbon  Vapours  by 
Method  of  Hempel  and  Dennis     .         .        .         .279 


XVi  CONTENTS 

PAGE 

4.  The  Volumetric  Analysis 282 

The  Volumetric  Analysis  of  Illuminating  Gas          .  282 

The  Volumetric  Analysis  of  Generator  Gas     .         .  290 
Determination  of  Hydrogen  and  Methane  by  Method 

of  Dennis  and  Hopkins         .....  293 

5.  The  Determination  of  Sulphur         .         .        .         .303 

6.  The  Determination  of  Ammonia      ....  308 

7.  The  Determination  of  Carbon  Dioxide     .        .         .  309 

CHAPTER   III 

ACETYLENE  GAS      .........  312 

Impurities  in  Acetylene  Gas     ......  313 

Volumetric  Analysis  of  Acetylene  Gas     ....  313 

Separation  of  Phosphine  from  Acetylene          .        .        .  315 

CHAPTER  IV 

GASES  WHICH  OCCUR  IN  THE  MANUFACTURE  OF  SULPHURIC 

ACID 322 

1.  Sulphur  Dioxide 322 

2.  Nitrous  Oxide 326 

3.  Nitric  Oxide 326 

4.  Nitrogen  Trioxide 326 

5.  Nitrogen  Peroxide 327 

6.  Oxygen 327 

CHAPTER  V 

ANALYSIS  OF  THE  GASES  EVOLVED  IN  THE  ELECTROLYSIS  OF 

CHLORIDES  328 


CHAPTER  VI 

DETERMINATION  OF  THE  GASES  WHICH  OCCUR  IN  THE  MANU- 
FACTURE OF  BLEACHING  POWDER     ....     330 

1.  Determination  of    the   Amount  of  Chlorine  in  the 

Chamber-air 330 

2.  Determination  of  Chlorine  in  the  Presence  of  Hydro- 

chloric Acid  Gas  331 


CONTENTS  xvii 


CHAPTER   VII 

PAGE 

THE  ANALYSIS  OF  ATMOSPHERIC  AIR 333 

1.  The  Determination  of  Aqueous  Vapour  in  the  Atmos- 

phere           333 

2.  The  Determination  of  Carbon  Dioxide  in  the  Atmos- 

phere          336 

3.  The  Determination  of  Carbon  Monoxide  in  the  Atmos- 

phere   370 

4.  The  Determination  of  Oxygen  in  the  Atmosphere       .  370 

5.  The  Determination  of  Ozone  in  the  Atmosphere          .  374 

6.  Argon  in  the  Atmosphere    ......  374 

7.  The  Determination  of  Sulphur  Dioxide  and  Sulphuric 

Acid  in  the  Atmosphere  ......  374 

8.  Nitrogen  in  the  Atmosphere 375 


CHAPTER   VIII 

EXAMINATION    OF    THE    GASES    AVHICH    ARE    PRODUCED    BY 

LIVING  BACTERIA  .  376 


CHAPTER   IX 

THE    DETERMINATION    OF    FLUORINE    AS     SILICON    TETRA- 

FLUORIDE  ........  .     378 


CHAPTER  X 

APPARATUS  FOR  THE  ANALYSIS  OF  SALTPETER  AND  THE 
NITRIC  ACID  ESTERS  (NITRQ-GLYCERIN,  GUN-COTTON, 
ETC.) 386 


CHAPTER   XI 

THE  DETERMINATION  OF  CARBON  AND  HYDROGEN  AND  THE 
SIMULTANEOUS  VOLUMETRIC  DETERMINATION  OF  NITRO- 
GEN IN  THE  ELEMENTARY  ANALYSIS  OF  ORGANIC  SUB- 
STANCES .  .  ....  .  392 


xviii  CONTENTS 

CHAPTER  XII 

PAGK 

A  CALORIMETRIC  METHOD  FOR  THE  DETERMINATION  OF  THE 

HEATING  POWER  OF  FUEL 411 

CHAPTER   XIII 

THE  DETERMINATION  OF  THE  HEATING  POWER  OF  GASES    .     435 
The  Flame  Calorimeter 442 

CHAPTER  XIV 

THE   DETERMINATION  OF  SULPHUR  IN  COAL  AND  ORGANIC 

SUBSTANCES 444 

CHAPTER  XV 

THE   RECOGNITION  AND   DETERMINATION  OF   METHANE   BY 

MEANS  OF  THE  FLAME  TEST 448 

CHAPTER  XVI 
THE  GAS  LANTERN 452 

CHAPTER  XVII 
THE  VOLUMETRIC  DETERMINATION  OF  CARBON  IN  IRON       .     459 

CHAPTER  XVIII 

THE  VOLUMETRIC  DETERMINATION  OF  THE  STRENGTH  OF 
"CHLORIDE  OF  LIME,"  PYROLUSITE,  POTASSIUM  PER- 
MANGANATE, AND  HYDROGEN  PEROXIDE,  AND  OF  THE 
AMOUNT  OF  CARBON  DIOXIDE  IN  SODIUM  CARBONATE  .  468 


CONTENTS  xix 

PAGE 

TABLE  OF  ATOMIC  WEIGHTS 475 

TABLE  FOR  THE  REDUCTION  OF  A  GAS  VOLUME  TO  0°  AND 

760  MM 476-479 

TABLE  GIVING  THE  TENSION  OF  AQUEOUS  VAPOUR  AT  DIF- 
FERENT TEMPERATURES    .         .         .         .  *  .      480-481 

TABLE  OF  THEORETICAL  DENSITIES  OF  GASES       .         .        .     482 
INDEX  483 


PART  I 
GENEEAL  METHODS 


CHAPTER  I 
THE  COLLECTING  AND  KEEPING  OF  GASES 

IN  gas  analysis,  as  in  all  other  analytical  work, 
the  proper  taking  of  the  sample  is  one  of  the  most 
important  operations.  Notwithstanding  the  rapid 
movement  of  gas  molecules,  currents  of  gases  are 
often  of  varying  composition,  especially  when  chemi- 
cal processes  are  simultaneously  going  on.  On  this 
account  the  place  at  which  the  samples  of  gas  are 
taken  is  of  the  greatest  significance.  In  pipes  or 
other  channels  the  point  of  smallest  cross-section  is 
the  most  suitable.  In  the  examination  of  furnace 
gases  it  is  best  to  take  the  sample  at  the  point 
where  the  visible  flame  ends,  because  farther  away, 
on  account  of  the  porosity  of  the  wall,  considerable 
quantities  of  air  are  always  mixed  with  the  gases 
from  the  fire.  To  take  the  sample,  an  iron  tube  is 
introduced  into  the  furnace  at  a  suitable  point.  A 
small  lead  pipe,  such  as  is  used  for  pneumatic  bells, 
is  attached  to  the  outer  end  of  the  iron  tube  by 
means  of  a  piece  of  rubber  tubing.  At  temperatures 
under  300°  the  lead  pipe  itself  may  be  inserted  into 
the  furnace.  The  great  advantage  possessed  by  such 
lead  pipe  is  that  it  is  very  small  internally  and  can 
be  manipulated  as  easily  as  rubber  tubing.  For  very 
high  temperatures  either  porcelain  tubes  or  cooled 

3 


4  GAS  ANALYSIS  PART  i 

iron  tubes  may  be  used.  With  acid  gases  glass 
tubes  should  be  employed  if  possible. 

Long  rubber  tubes  must  be  avoided,  but  short 
pieces  may  safely  be  used  for  connections.  Rubber 
receivers  also  are  to  be  rejected.  Vulcanised  rubber 
acts  toward  gases  as  does  a  liquid,  absorbing  the 
gases,  and  later,  according  to  the  prevailing  pressure, 
giving  them  up  again.  For  example,  a  piece  of 
rubber  tubing,  3  cm.  long  and  from  4  to  5  mm.  ex- 
ternal diameter,  absorbed  0.2  ccm.  of  carbon  dioxide 
and  0.9  ccm.  of  nitrous  oxide,  and  on  lying  in  the 
air  it  gradually  gave  up  these  gases. 

A  rubber  balloon  of  about  150  ccm.  capacity,  which 
was  filled  with  nitrogen  wholly  free  from  oxygen,  con- 
tained after  one  hour  1  per  cent  of  oxygen,  and  after 
six  and  one-half  hours  4J  per  cent  of  oxygen.  The 
experiments  of  Harbeck  and  Lunge  show  that  even 
very  thick  rubber  connections  allow  small  quantities 
of  gases  to  pass  through  the  walls.1  These  authors 
state  that  rubber  is  made  much  more  impervious  to 
the  passage  of  gases  by  coating  it  with  copal  varnish. 

If  the  place  where  the  gases  are  to  be  collected  is 
directly  accessible,  as,  for  example,  in  the  examina- 
tion of  mine  gases,  the  small  "medicine  bottles"2 
proposed  by  Bunsen  may  be  used,  the  neck  of  the 
bottle  being  drawn  out  in  the  flame  of  the  blast-lamp 
as  in  Fig.  1.  Bunsen  states3  that  the  bottle  should 
first  be  carefully  heated  between  the  shoulder  and 

1  Zeitschr.  f.  anorganische  Chemie,  16,  30. 

2  These  so-called  medicine  bottles  are  common  glass  bottles  about 
12  cm.  high.     They  were  recommended  by  Bunsen  because  they 
can  be  found  almost  everywhere,  even  small  village  drug  stores 
having  a  supply  of  them. 

8  Bunsen,  Gasometrische  Methoden,  2d  ed.  p.  12. 


CHAP,  i     COLLECTING  AND  KEEPING  OF   GASES 


the  neck,  and  the  neck  then  drawn  out  by  means  of 
suitable  tongs  (Fig.  2).  To  fill  the  bottle  with  gas, 
the  air  in  the  bottle  is  sucked  out  through  a  small 
glass  tube  reaching  to  the  bottom,  this  operation 
being  repeated  until  the  air  originally  in  the  bottle 
is  completely  replaced  by  gas  from  outside.  Five  or 
six  full  breaths  are  sufficient.  It  is  self-evident  that 
at  each  exhalation  of  the  air  sucked  from  the  bottle, 
one  must  step  aside  from  the  spot  where  the  gas 


FIG. 1. 


FIG.  2. 


FIG.  3. 


sample  is  being  taken.  The  tightly  stoppered  bottle 
is  then  slightly  warmed  over  a  spirit  lamp,  and  equi- 
librium between  the  expanding  air  inside  the  bottle 
and  the  outside  atmosphere  is  reestablished  by  lifting 
the  cork  for  a  moment.  After  cooling,  the  dimin- 
ished pressure  inside  the  bottle  prevents  the  blow- 
ing-out of  the  glass  when  the  narrow  neck  is  fused 
together.  The  fusion  may  conveniently  be  performed 
with  the  blow-pipe  shown  in  Fig.  3.  The  small 


6  GAS  ANALYSIS  PARTI 

lamp  a  holds  about  3  g.  of  oil,  and  is  connected 
with  the  blow-pipe  by  means  of  a  flexible  wire  that 
carries  a  collar  b  through  which  the  tip  of  the  blow- 
pipe is  inserted. 

The  cork  c  serves  as  a  mouth-piece  by  means  of 
which  the  whole  apparatus  can  be  held  and  guided 
by  the  teeth  alone.  Thus  both  hands  are  left  free, 
and  the  flame  can  still  be  moved  in  all  directions, 
since  the  relative  positions  of  the  blow-pipe  tip  and 
the  lamp  remain  the  same,  however  the  instrument 
be  held. 

In  actual  practice,  however,  it  has  been  found 
difficult  to  draw  out  the  neck  of  a  bottle  without 
cracking  it,  and  therefore  these  small  sampling  tubes 
had  best  be  made  in  the  laboratory  from  easily 
fusible  glass  tubing. 

The  arrangement  used  by  the  author  in  his  re- 
searches "upon  the  composition  of  the  atmosphere 
at  different  parts  of  the  earth "  is  also  a  very  con- 
venient one.  The  air  was  collected  in  glass  tubes 
of  the  form  shown  in  Fig.  4.  d  is  about  4  mm. 
thick;  a,  6,  and  0,  only  1  mm.  These  tubes  were 

heated  in  an  air-bath 
in  the  laboratory  to 
200°,  and  were  then 
exhausted  with  the 

mercury  air-pump  and  fused  together  at  c.  By 
simply  breaking  the  tube  at  5,  it  fills  instantly  and 
completely  with  the  air  in  question.  The  tubes  are 
then  closed  for  a  few  moments  with  a  rubber  cap, 
and  are  melted  together  at  a  over  a  candle.  The 
exhausting  with  the  air-pump  has  the  advantage  of 
rendering  one  less  dependent  upon  the  care  of  the 


CHAP,  i     COLLECTING  AND   KEEPING  OF   GASES  7 

person  who  fills  the  tubes.     If,  however,  it  is  desired 

to  avoid  this  exhausting,  the  tubes  are  given  the 

following  form  (Fig.  5  a). 

To  fill  such  a  tube,  the 

gas    to    be    examined    is  Fio.sa. 

drawn  through  it  and  the  tube  is  then  fused  together 

at  a  and  b  in  a  candle  flame  (Fig.  55). 

Such  tubes  can  be  most  safely  shipped  by  packing 
them  in  sawdust  in  boxes  which  have  a  separate 
compartment  for  each  tube.  The  boxes  themselves 
are  placed  in  a  larger  box  filled  with  hay. 

The  tube  last  described  is  filled  by  the  displace- 
ment of  the  air  already  contained  therein.  Naturally 


FIG.  5Z>. 

it  is  here  presupposed  that  large  amounts  of  gas  are 
at  one's  disposal.  If  only  a  small  quantity  of  gas  is 
obtainable,  the  receiver  must  be  filled  with  water  or 
mercury,  which  is  then  displaced  by  the  gas.  If  it 
is  possible  to  analyse  the  gas  samples  within  a  short 
time  after  their  collection,  we  may  employ  small 
glass  tubes  of  the  form  shown  in  Fig.  6.  Such 
tubes  may  conveniently  be  used  for  the  examination 
of  the  air  in  coal  mines.  Water  can  be  used  only 
when  it  is  first  saturated  with  the  gases  in  question, 


GAS  ANALYSIS 


PART  I 


as,  for  example,  is  always  the  case  with  the  water  of 
bubbling  springs. 


To  collect  gas  from  such  springs  as  are  directly 
accessible,  the  small  apparatus  proposed  by  Bunsen 1 
is  used  (Fig.  7). 

This  consists  of  a  test-tube  c 
of  from  40  to  60  ccm.  capacity, 
drawn  out  at  a  before  the  blast- 
lamp  to  the  size  of  a  fine  straw, 
and  connected  air-tight  with 
the  funnel  b  by  means  of  a  well- 
fitting  cork  or  a  piece  of  vul- 
canised rubber  tubing.  Instead 
of  the  test-tube  a  small  long- 
necked  medicine  bottle  may  be 
used,  this  being  drawn  out  in 
the  middle  of  the  neck  to  a 
similar  strawlike  contraction. 
The  apparatus  is  then  filled 
with  the  water  of  the  spring. 
This  cannot  be  done  without 
access  of  air,  which  would  change  the  composition 
of  the  gases  diffused  through  the  spring  water  in 
the  tube.  Hence  the  inverted  apparatus,  with  the 
mouth  of  the  funnel  upward,  is  lowered  below  the 
level  of  the  spring,  and,  with  a  narrow  tube  reaching 

1  Bunsen,  Gasometrische  Methoden,  2d  ed.  p.  2. 


FIG.  7. 


CHAP,  i     COLLECTING  AND   KEEPING   OF   GASES  9 

to  the  bottom  of  the  test-tube,  the  water  which  in 
the  first  filling  had  come  in  contact  with  the  air  is 
sucked  out  until  one  is  satisfied  that  it  has  been 
entirely  replaced  by  other  water  from  the  spring. 
If  now  the  gas  of  the  spring  is  allowed  to  rise 
through  the  funnel  into  the  test-tube  thus  filled, 
the  purity  of  the  sam- 
ple is  assured.  If  the 
rising  bubbles  stop  in 
the  neck  of  the  funnel 
or  at  the  contraction 
a,  they  can  easily  be 
made  to  ascend  by  tap- 
ping the  edge  of  the 
funnel  upon  some  hard 
substance.  The  appa- 
ratus is  then  placed  in 
a  small  dish  and  re- 
moved from  the  spring, 
and  the  tube  is  melted 
together  at  a.  This 
can  easily  be  done 
with  the  blow-pipe, 
the  moisture  at  the 
point  a  having  first 
been  driven  away  by 
warming. 

W.  Ramsay  and  M. 
W.  Travers  have  pro- 
posed the  apparatus 

\  .         „.  ,.  FIG.  8. 

shown   in    Fig.    8   for 

collecting   large   quantities   of   gases   from   mineral 

waters.    The  cylinder  A  is  filled  with  the  water  of 


10 


GAS   ANALYSIS 


the  spring,  and  the  rising  bubbles  of  gas  pass  into 
the  cylinder  through  the  funnel  D  and  the  tube  C. 

For  the  determination  of  the  volume  and  compo- 
sition of  the  absorbed  gases  in  liquids,  the  Tiemann 
and  Preusse  modification  of  Reichardt's  apparatus  1 
can  be  recommended  (Fig.  9). 

This  consists  of  two  flasks  A  and  B,  each  of  about 
1  liter  capacity,  and  connected  by  tubes  with  the  gas- 


FIG.  9. 

collector  <7.  The  flask  A  is  fitted  with  a  per- 
forated rubber  stopper  in  which  is  inserted  the  glass 
tube  a  bent  at  a  right  angle  and  ending  flush  with 
the  lower  surface  of  the  stopper,  a  is  joined  by  a 
piece  of  rubber  tubing  to  the  tube  5<?,  which  in  turn 
connects  with  the  gas-collector  C.  C  is  held  by  a 
clamp,  has  a  diameter  of  35  mm.,  is  about  300  mm. 

1  Berichte  der  deutschen  chemischen  GesellscJiaft,  1879,  p.  1768. 


CHAP,  i     COLLECTING  AND   KEEPING  OF   GASES  11 

long,  and  at  the  upper  end  is  drawn  out  to  a  short, 
narrow,  and  slightly  bent  tube  which  can  be  closed 
with  the  rubber  tube  and  pinchcock  g.  In  the  lower 
end  of  O  is  a  rubber  stopper  with  two  holes  through 
one  of  which  the  tube  be,  projecting  about  80  mm. 
into  (7,  is  inserted.  Through  the  other  opening  passes 
the  tube  d  which  extends-  only  slightly  beyond  the 
stopper  and  connects  0  with  the  flask  B.  B  has  a 
double-bore  rubber  stopper  carrying  the  tubes  e  and/. 
e  ends  about  10  mm.  above  the  bottom  of  the  flask, 
and  above  the  stopper  it  is  bent  at  a  right  angle  and 
is  connected  with  d.  The  tube  /,  which  need  not 
project  below  the  stopper,  carries  a  thin  rubber  tube 
x  about  1  m.  in  length  and  provided  with  a  mouth- 
piece. A  pinchcock  for  closing  the  rubber  tube 
between  a  and  b  is  also  needed. 

The  apparatus  thus  arranged  is  made  ready  for  a 
determination  by  filling  the  flask  B  somewhat  more 
than  half  full  of  boiled  water  and  removing  the  flask 
A  by  slipping  the  tube  a  out  of  the  rubber  connec- 
tion ;  then,  by  blowing  into  the  rubber  tube  x,  water 
is  driven  over  from  the  flask  B  into  the  gas-collector 
0  and  the  adjoining  tubes,  until  the  air  is  wholly  dis- 
placed. The  rubber  tubes  at  b  and  g  are  now  closed 
with  pinchcocks.  The  flask  A  is  then  filled  to  the 
brim  with  distilled  water,  the  stopper  is  inserted, 
water  being  thereby  driven  into  the  tube  #,  and  the 
flask  is  again  connected  with  6,  the  pinchcock  being 
opened. 

The  water  in  B  is  now  heated  to  gentle  boiling, 
and  that  in  A  is  allowed  to  boil  somewhat  more 
rapidly.  The  absorbed  air  is  thus  driven  out,  and 
the  gases  which  are  dissolved  in  the  water  in  A  and  0 


12  GAS   ANALYSIS  PART  i 

collect  in  the  upper  part  of  (7,  from  which  they  are 
removed  by  occasionally  opening  the  pinchcock  at  g 
and  blowing  into  the  rubber  tube  x. 

When,  upon  cooling  the  apparatus,  the  gases  which 
have  collected  disappear,  the  heating  of  the  flask  A  is 
discontinued,  the  pinchcock  between  a  and  b  is  closed, 
and  A  is  disconnected  and  emptied.  The  water  in 
O  and  B  is  now  entirely  free  from  absorbed  gases, 
and  air  cannot  enter  from  without  because  the  liquid 
in  B  is  kept  continually  boiling.  The  apparatus  is 
now  ready  for  a  determination,  which  is  made  as 
follows  :  — 

The  cooled  flask  A,  whose  capacity  has  been  previ- 
ously determined,  is  filled  with  the  water  to  be  exam- 
ined, and  the  stopper  is  pressed  in  so  far  that  the  air 
in  the  tube  a  is  completely  driven  out.  a  is  then 
connected  with  6,  care  being  taken  that  in  so  doing 
no  air-bubbles  are  enclosed.  The  pinchcock  between 
a  and  b  is  opened,  and  the  water  in  A  is  heated  to 
gentle  boiling  The  dissolved  gases  are  hereby  driven 
over  into  the  gas-collector  0.  Steam  is  formed  at 
the  same  time.  The  heating  of  the  flask  A  must 
now  be  so  regulated  that  the  gas  and  steam  evolved 
never  drive  out  more  than  half  the  liquid  in  0: 
otherwise  there  is  danger  of  gas-bubbles  entering  the 
tubes  d  and  e  and  thus  escaping. 

After  heating  for  about  twenty  minutes,  the  flame 
under  A  is  removed.  In  a  few  minutes  the  steam  in 
A  and  O  condenses,  and  water  passes  from  B  toward 
Q  and  A.  If  a  gas-bubble  is  observed  in  A,  the  flask 
A  must  again  be  heated  and  cooled  in  the  manner 
just  described.  The  operation  is  ended  when  the  hot 
liquid  flows  back  and  completely  fills  A.  The  rubber 


CHAP,  i     COLLECTING  AND   KEEPING  OF   GASES  13 

tube  g  is  then  connected  with  a  small  tube  which  is 
filled  with  water  or  mercury,  and  the  gas  standing 
over  the  hot  liquid  in  C  is  driven  over  into  a  eudi- 
ometer, gas  burette,  or  gasometer  by  blowing  into  the 
tube  x  and  opening  the  pinchcock  g. 


FIG.  10. 

F.  Hoppe-Seyler l  has  devised  a  somewhat  more 
complicated  apparatus  for  extracting  the  absorbed 
gases  from  the  waters  of  springs  and  rivers.  It  is  a 
modification  of  the  method  proposed  by  Bunsen  and 
Dittmar.  The  apparatus  shown  in  Fig.  10  varies 
slightly  from  that  suggested  by  Hoppe-Seyler  in  that 

1  Zeitschr.  f.  analyt.  Chem.  31,  367. 


14  GAS   ANALYSIS  PART  i 

a  gas  burette  D  (see  page  35)  is  used  as  the  collect- 
ing vessel  and  air-pump.  Any  other  burette  with  a 
two-way  stopcock  may,  of  course,  be  employed  in 
place  of  the  burette  here  figured.  The  apparatus 
consists  of  the  gas  burette  D  filled  with  mercury,  the 
glass  tubes  A,  B,  and  C  and  the  level-bulb  F.  The 
tubes  .A,  B,  and  O  are  joined  together  with  pieces  of 
rubber  tubing.  Screw  pinchcocks  are  placed  at  a 
and  b.  To  extract  the  dissolved  gases  from  a  sample 
of  water,  a  bent  glass  tube  is  inserted  at  b  and  the 
tubes  A  and  0  are  filled  with  mercury  by  raising  the 
level-bulb  JP,  the  mercury  being  allowed  to  rise  until 
it  reaches  the  tube  which  has  been  inserted  at  b. 
The  glass  tube  is  then  introduced  into  the  vessel 
which  contains  the  water  to  be  examined,  and  by 
lowering  the  level-bulb  F  water  is  drawn  into  the 
apparatus  until  the  tube  A  is  completely  filled  with 
it.  The  bent  tube  is  then  removed  from  5,  B  is  in- 
serted in  its  place,  and  the  pinchcock  at  b  is  closed. 
The  two-way  stopcock  of  the"  burette  is  now  turned 
so  that  the  burette  communicates  with  the  exit 
tube  f.  The  air  in  the  burette  is  driven  out  by 
raising  the  level-bulb  E,  and  the  stopcock  g  is  then 
turned  so  that  the  burette  communicates  with  the 
tube  B.  Upon  lowering  the  level-bulb  as  far  as  pos- 
sible the  burette  may  now  be  made  to  function  as  a 
mercury  air-pump  and  the  air  which  is  in  B  can  be 
drawn  over  into  D.  Upon  closing  the  stopcock  #, 
raising  the  bulb  JH,  and  then  turning  G-  so  that  the 
burette  communicates  with  f,  the  air  which  has  been 
drawn  out  of  B  may  be  expelled  from  the  burette. 
This  operation  is  then  repeated  until  no  more  bubbles 
of  gas  appear.  When  the  tube  B  has  thus  been  ex- 


CHAP,  i     COLLECTING   AND   KEEPING   OF   GASES  15 

hausted  of  air,  the  cocks  #,  Z>,  and  c  are  opened,  and 
the  water  in  the  apparatus  is  brought  to  boiling 
by  heating  the  tubes  A  and  C  directly  with  the 
Bunsen  burner.  The  escape  of  the  gas  into  the 
vacuum  of  B  begins  at  once.  After  about  five  min- 
utes, the  water  in  A  is  brought  nearly  to  the  height 
of  the  pinchcock  b  by  raising  or  lowering  the  level- 
bulb  F.  b  is  then  closed  and  the  gas  in  B  is  pumped 
out  by  raising  and  lowering  the  level-bulb  E  in  the 
manner  above  described.  /  is  connected  by  means 
of  a  bent  capillary  tube  with  a  second  gas  burette  or 
gas  pipette,  and  the  gas  which  has  been  drawn  over 
into  D  from  B  is  transferred  to  the  second  gas  holder 
by  turning  g  so  that  D  communicates  with  /.  The 
pinchcock  b  is  then  opened,  the  water  in  A  is  again 
brought  to  boiling,  and  the  gas  set  free  by  this  second 
treatment  is  added  to  the  portion  first  obtained.  By 
repeating  the  process  three  times  it  is  easily  possible 
to  completely  extract  all  of  the  absorbed  gases  with 
the  exception  of  carbon  dioxide.  This  latter  gas  is 
so  persistently  retained  by  the  water  that  according 
to  the  experiments  of  Jacobsen  it  is  impossible  to  en- 
tirely remove  it.  Pettersson  has  shown  that  even 
after  strongly  acidifying  the  water  with  sulphuric 
acid  the  carbon  dioxide  cannot  be  completely  driven 
out  by  boiling. 

Gases  are  set  free  in  many  chemical  reactions  that 
take  place  in  sealed  tubes.  If  one  wishes  to  examine 
these  gases,  Bunsen  directs 1  that  when  the  tube  is 
fused  together,  it  be  drawn  out  to  a  fine  tip  about 
2  mm.  wide  and  50  mm.  long.  To  collect  the  gases 
given  off,  a  mark  is  made  at  a  with  a  sharp  file,  and 

1  Bunsen,  Gasometrische  Methoden,  2d  ed.  p.  10. 


16  GAS  ANALYSIS  PART  i 

the  tip  is  connected  with  a  capillary  glass  tube  by 
means  of  a  short  piece  of  rubber  tubing  (Fig.  11). 

For  safety's  sake  wire  ligatures  are  put  on  at  b 
and  c.  On  breaking  the  tube  inside  the  rubber  at 
a,  the  gas  passes  through  the  delivery  tube  and  can 
be  collected  in  any  desired  receiver.  If  very  strong 
pressure  in  the  tube  is  to  be  expected,  the  rubber 


PIG.  11. 


connection  is  surrounded  with  a  strip  of  linen,  and 
the  tube  itself  is  wrapped  in  a  cloth.  A  third  ligature 
put  on  at  d  makes  it  possible  to  stop  the  escape  of 
gas  at  any  time,  the  rubber  forming  with  the  broken- 
off  glass  tube  a  Bunsen  rubber  stopcock. 

To  extract  the  gases  which  may  be  present  in  min- 
erals or  stones,  Ramsay  and  Travers  recommend 
that  the  mineral  be  first  reduced  to  a  fine  powder 


CHAP,  i     COLLECTING  AND  KEEPING  OF   GASES  17 

and  be  then  mixed  with  double  its  weight  of  primary 
potassium  sulphate.  The  mixture  is  placed  in  a 
hard-glass  tube  which  is  connected  with  an  air- 
pump.  After  the  tube  has  been  exhausted  it  is 
heated  to  redness  with  a  large  Bunsen  burner.  The 
escaping  gases  are  pumped  out  and  are  collected  in  a 
small  tube  which  contains'some  potassium  hydroxide. 
In  order  to  exclude  the  possibility  of  leakage,  the 
tube  is  joined  to  the  air-pump  in  the  manner  shown 
in  Fig.  12.  As  may  be  seen  from  the  drawing,  the 


FIG.  12. 

large  tube  is  drawn  out  at  A,  a  piece  of  rubber  tub- 
ing is  placed  over  the  end  of  the  small  tube  B,  and 
after  it  has  been  inserted  in  the  contraction  at  A,  the 
joint  is  covered  with  mercury  standing  in  the  wide 
portion  0.  In  most  cases  the  gases  which  are  present 
in  the  mineral  are  driven  out  by  heating  the  sub- 
stance alone  without  the  addition  of  primary  potas- 
sium sulphate. 

If  one  wishes  to  extract  only  those  gases  which 
are  mechanically  enclosed  in  a  mineral  or  metal,  the 


18 


GAS  ANALYSIS 


problem  becomes  much  more  difficult,  since  chemical 
changes  in  the  substance  may  easily  occur  when 
it  is  heated.  Thus  carbonates  will  lose  carbon 
dioxide,  while  ferrous  salts  are  able  to  reduce  carbon 
dioxide  to  carbon  monoxide  and  water  vapour  to 
hydrogen.  The  procedure  devised  by  the  author  to 
meet  such  cases  is  as  follows  :  A  large  piece,  B,  of 

the*  mineral  or  metal  in 
question  is  placed  in  a  cyl- 
inder A  (Fig.  13)  made  of 
heavy  sheet  iron  and  the 
space  between  the  sample 
and  the  cylinder  is  filled 
with  plaster  of  Paris. 
Mercury  is  then  poured 
on  the  top  of  the  sample 
until  it  is  covered  with  a 
layer  about  4  cm.  thick. 
By  means  of  a  hollow  steel 
drill,  closed  at  the  top  and 
filled  with  mercury,  a  hole 
of  desirable  depth  is  bored 
in  the  top  of  the  sample, 
the  drill  being  driven  in 
by  means  of  a  hammer  and 
being  frequently  slightly  raised  and  turned  during 
the  procedure.  Its  lower  end  must,  of  course,  never 
be  raised  above  the  level  of  the  mercury.  The 
powder  from  the  drilling,  together  with  the  gases  in 
the  sample,  collect  inside  the  steel  drill  and  are 
removed  from  the  latter  in  the  manner  described 
below. 

The  drill  may  best  be  made  by  boring  out  a  solid 


FIG.  13. 


CHAP,  i     COLLECTING  AND  KEEPING  OF   GASES  19 

bar  of  steel  and  the  lower  edge  is  then  notched.  In 
order  to  pulverise  the  particles  of  the  sample  as 
finely  as  possible  during  the  drilling,  a  notched  cross- 
piece  is  inserted  into  the  open  end  of  the  drill  tube. 
To  fill  the  drill  with  mercury,  it  is  placed  open 
end  up  and  a  straight  glass  adapter  is  pushed  over 
the  open  end  of  the  drill  and  fastened  in  place  by 
a  rubber  ring.  The  drill  and  adapter  are  then 
completely  filled  with  mercury,  the  open  end  is 
closed  with  the  finger,  and  the  tube  is  inverted  in  a 
deep  vessel  filled  with  mercury.  The  adapter  and 
rubber  ring  are  then  slipped  off,  a  shallow  dish  is 
brought  under  the  end  of  the  drill,  and  the  latter  is 
then  transferred  to  the  cylinder  A,  the  dish  being 
removed  after  the  mouth  of  the  drill  has  been  brought 
under  the  mercury  in  A.  In  this  manner  it  is  easy 
to  completely  fill  the  drill  with  mercury.  The  layer 
of  gas  which  persistently  adheres  to  all  larger  sur- 
faces is  not  removed  from  the  drill  when  the  latter 
is  filled  with  mercury,  and  for  this  reason  a  small 
quantity  of  air  is  always  present  in  the  gases  which 
have  been  set  free  from  the  mineral  during  the  drill- 
ing. In  order  to  eliminate  this  error  in  the  analysis 
two  determinations  must  always  be  made.  In  the 
first,  the  amount  of  carbon  dioxide  in  the  gas  mix- 
ture is  accurately  determined.  The  small  amount  of 
this  constituent  which  is  present  in  the  air  can  be. 
disregarded  when  dealing  with  such  small  quantities 
of  gas  as  are  here  in  question.  In  the  second  ex- 
periment, carbon  dioxide  is  passed  into  the  drill  and 
into  the  apparatus  (see  below)  that  is  designed  to 
receive  the  gases  from  the  drill,  until  the  layer  of 
gas  first  adhering  to  the  surface  has  been  completely 


20  GAS  ANALYSIS  PART  i 

driven  out  by  the  carbon  dioxide,  and  all  air  has 
thus  been  expelled.  In  carrying  out  this  opera- 
tion, the  author  always  uses  a  cylinder  charged  with 
liquid  carbon  dioxide  because  this  is  much  purer 
than  that  which  is  evolved  by  the  action  of  acid 
upon  marble.  Ordinary  marble  is  so  porous  that 
appreciable  quantities  of  air  are  always  set  free  with 
carbon  dioxide  when  it  is  treated  with  an  acid. 

To  now  remove  both  the  gases  which  have  col- 
lected, as  well  as  the  powdered  mineral  in  the 
hollow  drill,  a  shallow  dish  is  slipped  under  the 
mouth  of  the  drill,  the  latter  is  lifted  from  the  cylin- 
der A)  the  dish  is  placed  upon  the  ring  of  an  ordi- 
nary iron  stand,  and  the  drill  is  fastened  in  a  clamp 
so  that  it  stands  in  a  perpendicular  position.  The 
outside  of  the  drill  is  now  washed  with  a  stream  of 
water  to  remove  any  powdered  mineral  adhering  to 
it,  for  the  presence  of  this  powder  might  prevent  a 
gas-tight  joint  between  the  outer  surface  of  the  drill 
and  the  rubber  ring  which  is  to  be  slipped  over  it. 
The  drill  and  dish  are  then  placed  in  a  deep  vessel 
filled  with  mercury,  the  dish  is  removed,  and  a  rub- 
ber ring  is  slipped  over  the  lower  end  of  the  drill. 
A  glass  adapter  is  then  pushed  on  to  the  rubber 
ring,  the  operation,  of  course,  being  carried  on  under 
the  level  of  the  mercury.  In  the  meantime,  the 
apparatus  into  which  the  gas  is  to  be  drawn  off 
(Fig.  14)  has  been  filled  with  mercury  to  such  a 
height  that  the  inverted  half -bottle  JE  is  completely 
filled.  A  rubber  band  is  now  slipped  over  the  lower, 
narrow  end  of  the  adapter  J.  This  end  is  then  closed 
with  the  finger,  and  drill  and  adapter  are  transferred 
to  the  mercury  contained  in  the  bottle  E,  the  end  of 


FIG.  14. 


FIG.  15. 


22  GAS   ANALYSIS  PART  i 

the  adapter  being  inserted  in  the  upper  end  of  the 
tube  F.  The  drill  is  now  fastened  firmly  in  posi- 
tion by  means  of  the  clamp,  and  upon  lowering  the 
level-bulb  Gr  the  inside  of  the  drill  is  brought  under 
diminished  pressure.  The  positions  of  the  various 
parts  of  the  apparatus  at  this  point  are  shown  in  Fig. 
14.  The  rubber  rings  at  b  and  c  are  rendered  com- 
pletely gas-tight  by  the  mercury  which  stands  over 
them.  Upon  connecting  the  stopcock  If  with  the 
mercury  air-pump,  the  gases  which  have  collected 
in  D  may  now  easily  be  removed  and  transferred  to 
another  vessel  for  analysis. 

The  taking  of  the  gas  sample  is  especially  difficult 
\vhen  at  the  same  time  the  disturbing  influences  of 
elevated  temperature,  chemical  action,  and  high  me- 
chanical pressure  must  be  overcome,  as  for  example 
in  the  collecting  of  gases  from  the  blast-furnace. 
Bunsen  and  Playfair,  in  their  investigation  at  the 
blast-furnace  in  Alfreton,  England,  introduced  a 
wrought-iron  tube  into  the  throat  of  the  furnace  and 
allowed  it  to  sink  with  the  charge.  The  tube  con- 
sisted of  five  pieces,  which  were  screwed  on  from 
time  to  time  as  the  tube  sank. 

Winkler  has  proposed1  the  device  shown  in  Fig.  15, 
the  form  here  given  being  that  used  by  Schertel  in 
his  investigations  on  the  Freiberg  lead  furnaces. 
They  both  used  three  tubes,  which  could  be  length- 
ened as  much  as  desired  by  screwing  on  additional 
pieces.  The  bottom  of  the  outer  tube  is  welded  on, 
and  into  it  the  two  inner  tubes  are  tightly  screwed ; 
b  has  a  number  of  side  openings  just  above  its  lower 

1  Clemens  Winkler,  Anleitung  zur  chemischen  Untersuchung  der 
Industrie- Gase,  Part  II,  p.  7. 


FIG.  16. 


24  GAS  ANALYSIS  PARTI 

end,  but  it  does  not  pass  through  the  bottom,  whereas 
a  does.  When  in  use,  a  stream  of  water  enters  at  b 
and,  passing  into  A,  surrounds  the  tube  a  and  pro- 
tects it  from  the  action  of  the  heat.  The  water  is 
led  off  at  c  by  a  rubber  tube.  The  stoppage  of  the 
tube  by  dust  is  prevented  by  putting  a  wad  of  as- 
bestos into  the  mouth  of  the  tube  a  while  the  appa- 
ratus is  being  introduced  into  the  furnace.  The 
tube  is  let  down  by  a  pulley  to  the  lowest  point  at 
which  the  gas  is  to  be  taken.  The  asbestos  stopper 
is  then  pushed  out  with  a  stiff  iron  wire.  To  take 
samples  of  gas  from  points  higher  up,  the  tube  is 
simply  drawn  up  the  desired  distance. 

If  the  gases  to  be  collected  have  a  pressure  less 
than  the  prevailing  atmospheric  pressure,  an  aspirator 
must  be  used.  The  simplest  form  consists  of  two  in- 
terchangeable bottles  of  equal  size  and  the  same  width 
of  neck.  Figure  16  shows  an  arrangement  which 
may  be  used  when  one  wishes  to  take  samples  at  the 
same  time  in  a  gas  burette  (see  p.  35).  The  water 
passes  from  the  bottle  A  through  the  siphon  Gr  into 
(7,  and  thereby  draws  the  gas  from  the  tube  F. 
When  A  is  empty,  (7,  which  is  now  full,  is  put  in  its 
place,  the  aspirating  of  the  gas  continuing  as  long  as 
the  samples  are  being  taken. 


FIG.  IT. 


Small   rubber   pumps    are    also    very    convenient 
(Fig.  17).     These  act  both  as  suction  and  pressure 


CHAP,  i     COLLECTING  AND  KEEPING  OF  GASES 


25 


pumps.  The  thick-walled  bulb  A  is  supplied  with 
two  simple  valves  working  opposite  to  each  other. 
When  the  bulb  is  compressed  with  the  hand,  press- 
ure is  produced  in  one  of  the  tubes,  and  when 
the  bulb,  through  the  elasticity 
of  the  rubber,  assumes  its  origi- 
nal form,  suction  on  the  other 
side  results.  Either  rubber 
valves  or  metallic  plug-valves 
are  used;  the  latter  have  the 
advantage  of  retaining  their 
efficiency  for  many  years.  It 
must  not  be  forgotten  that  gas 
mixtures  are  affected  by  the 
rubber,  and  that  on  this  ac- 
count the  apparatus  for  receiv- 
ing the  gas  must  be  put  before 
the  pump. 

When  running  water  is  at 
hand,  a  water  suction-pump 
may  be  used  with  advantage.  The  forms  proposed 
by  Finkener  (Fig.  18  a)  and  by  Geissler  (Fig.  18  6) 
are  among  the  simplest.  In  these  the 
water  passes  under  high  pressure  from  the 
narrow  tube  a  into  the  wider  tube  <?,  and 
acts  as  an  injector,  thus  sucking  air  in  at  6. 
A  more  durable  and  more  efficient  form 
of  water-pump  is  the  one  constructed  by 
Chapman.  This  is  entirely  of  brass  and 
has  the  form  shown  in  Fig.  19. 
With  such  an  apparatus  as  that  constructed  by 
Korting,1  steam  also  may  be  used  for  aspirating. 

1  Gebr.  Korting,  Hanover,  Germany. 


FIG.  18  a.       FIG.  18  5. 


FIG.  19. 


GAS   ANALYSIS 


PART  I 


An    aspirator    of    sheet    zinc    is    well    suited    to 
the    collecting    and    keeping    of    large    quantities 

of  gas.  It  consists  of  a 
large  cylindrical  vessel 
whose  conical  ends 
are  closed  air-tight 
by.  stopcocks  (Fig. 
20). 

If  gases  are  to  be 
taken  from  a  chamber 
in  which  excess  of 
pressure  prevails,  the 
gas  burettes  which 
will  be  described  later 
may  be  used  directly 
as  aspirators  by 
simply  inserting  in 
the  rubber  tube  at 
the  top  of  the  bu- 
rette a  small  '  glass 
tube,  filling  this  with 
water,  holding  it  in 
the  current  of  gas, 
and  then  drawing 
the  gas  into  the  burette  by  lowering  the  level- 
tube  and  opening  the  pinchcock  at  the  top  of  the 
burette. 

A  gas  can  be  best        _ 
kept    in    the    fused    <^^pg^       r===s 
glass   tubes    already  Fm  21 

described,  but  glass 

bulbs   supplied  with  two   glass  stopcocks  are   also 
quite  satisfactory  (Fig.  21). 


FIG.  20. 


CHAP,  i     COLLECTING  AND   KEEPING  OF   GASES 


27 


Metallic  receivers  should  be  used  for  analytical 
purposes  only  when  the  gas  is  to  remain  in  them  but 
a  short  time.  They  are,  however,  not  easily  broken, 
and  are  especially  well  adapted  to  the  transport  of 
large  quantities  of  gas. 

Rubber  sacks  should  never  be  employed,  since  gas 
mixtures  confined  in  them  rapidly  change  in  com- 
position. 


FIG.  22. 


If  large  amounts  of  gas  are  to  be  collected  and 
kept  for  analysis  for  a  considerable  length  of  time, 
the  portions  of  gas  taken  for  analysis  must  be  dis- 
placed with  mercury.  It  is  utterly  impracticable 
to  use  water  for  this  purpose,  for  continual  changes 
would  take  place,  since  the  absorption  varies  with  the 
pressure  and  temperature.  A  gasometer  which  for 


28 


GAS   ANALYSIS 


PART  I 


FIG.  23. 


years  past  has  given  good  satisfaction  in  the  Dresden 
laboratory  is  shown  in  Fig.  22.  The  large  glass  bulb 
A  serves  to  hold  the  gas.  At  the  top  it  carries  the 
bent  capillary  tube  #,  and  at  the  bottom 
it  is  joined  to  the  level-bulb  B  by  a  rub- 
ber tube.  The  capillary  is  closed  by  a 
rubber  tube  and  pinchcock.  The  appa- 
ratus is  first  filled  with  mercury.  By 
lowering  or  raising  the  level-bulb,  gas 
can  be  drawn  in  or  driven  out  as  desired. 
If  gases  are  to  be  kept  for  some  time,  the 
capillary  tube  a  is  filled  with  mercury  by  means  of  a 
little  pipette  inserted  at  c.  This  closes  the  bulb  per- 
fectly. In  such  an  appa- 
ratus gases  may  be  kept 
unchanged  for  an  unlimited 
time. 

Small  glass  bulbs  (Fig. 
23)  are  also  very  conven- 
ient. They  are  filled  with 
gas  in  a  mercury  trough, 
and  are  then  placed  mouth 
downward  in  small  porce- 
lain crucibles  containing 
mercury.  The  gas  is  taken 
out  with  the  gas  pipette  to 
be  described  later. 

A  convenient  gasometer 
may  be  easily  constructed 
from  a  round -bottomed 
flask  fitted  with  a  two-hole 
rubber  stopper  and  bent  glass  tubes  in  the  manner 
shown  in  Fig.  24. 


FIG.  24. 


CHAP,  i     COLLECTING  AND   KEEPING   OF   GASES 


29 


Larger  volumes  of  gas  may  be  collected  in  a  glass 
gasometer  of  the  form  shown  in  Fig.  25. l  This 
apparatus  is,  however, 
very  fragile,  and  since 
it  is  of  glass,  it  can- 
not be  made  in  large 
sizes.  The  reason  for 
the  peculiar  form  of 
gasometer  will  be 
found  in  the  descrip- 
tion of  Fig.  26. 

For  collecting  and 
keeping  large  sam- 
ples of  gas,  a  bell  gas- 
ometer made  of  zinc 
or  sheet  iron  and 
filled  with  a  concen- 
trated solution  of 
magnesium  chloride 
may  conveniently  be 
employed.  The  metal 
gasometers  ordinarily 
used  in  laboratories 
are  not  practical  because  the  gases  stand  over  large 
amounts  of  liquid  which  must  continually  be  re- 
newed in  the  filling  and  emptying  of  the  gasometer, 
with  the  result  that  the  gas  mixture  is  contaminated 
to  a  considerable  degree  by  the  gases  which  were 
present  in  the  confining  liquid.  Figure  26  shows 
an  arrangement  which  makes  it  possible  to  enclose 
large  quantities  of  gas  with  the  aid  of  a  small 

1  This  may  be  obtained  from  Ehrhardt  and  Metzger  of  Darm- 
stadt, Germany. 


FIG.  25. 


30 


GAS  ANALYSIS 


PART  1 


amount  of  a  confining  liquid.  The  gasometer  con- 
sists of  the  bell  A  which  dips  into  the  cylindrical 
ring-shaped  space  J5,  this  latter  being  filled  with  a 
solution  of  magnesium  chloride.  The  shaded  part 


FIG.  26. 


D  is  a  hollow  cylinder  closed  at  both  the  top  and 
bottom.  The  iron  tube  a  serves  as  a  guide  for  the 
bell  and  should  therefore  be  made  quite  wide.  The 
gasometer  is  filled  by  introducing  the  gas  in  question 


CHAP,  i     COLLECTING  AND  KEEPING   OF   GASES  31 

through  /.  A  branch  tube  at  e  extends  downward 
into  a  glass  cylinder  filled  with  water  and  serves  the 
double  purpose  of  enabling  the  operator  to  observe 
the  pressure  Q£  the  gas  and  to  drive  out  any  air  in 
the  tubes  through  this  branch.  The  weights  E  and 
F  make  it  possible  to  regulate  at  will  the  pressure 
in  the  gasometer.  When  the  gasometer  has  been 
filled,  the  rubber  tube  d  is  removed  from  c.  The 
gas  can  then  be  drawn  off  through  either  the  stop- 
cock b  or  c. 


CHAPTER   II 

GENERAL  REMARKS   UPON  THE   ANALYSIS   AND 
MEASUREMENT   OF   GASES 

FOR  the  analysis  itself  various  methods,  correspond- 
ing to  the  nature  of  the  gases,  suggest  themselves. 
The  gases  may  be  separated  — 

1.  By  successive  absorption  of  the  different  con- 
stituents and  the  volumetric  determination  of  each. 

2.  By  absorption  and  subsequent  determination  by 
titration  or  weighing. 

3.  By  combustion  and  the  volumetric  or  gravi- 
metric determination  of  the  products. 

Under  all  circumstances,  however,  the  first  opera- 
tion is  the  measuring  of  the  gas. 

From  the  nature  of  a  gas  it  is  clear  that  its  quan- 
tity can  generally  be  better  determined  by  measuring 
its  volume  than  by  ascertaining  its  weight.  Hence 
one  of  the  most  important  operations  in  gas  analysis 
is  the  measurement  of  gases. 

The  volume  of  a  gas  is  influenced  by  pressure, 
temperature,  and  the  tension  of  the  liquid  present. 

By  Boyle's  law  the  density  and  the  pressure  of  a 
gas  are  proportional  to  each  other. 

According  to  Gay-Lussac's  law  gases  expand  ^^ 
of  their  volume  at  0°  for  each  degree  of  temperature. 

The  tension  of  the  confining  or  absorption  liquid 
causes  an  increase  of  volume.  This  increase  is 

32 


CHAP,  ii  THE   ANALYSIS   OF   GASES  33 

dependent  upon  the  temperature,  is  independent  of 
the  pressure,  and  varies  with  the  chemical  nature  of 
the  liquid  in  question. 

To  reduce  a  gas  volume,  measured  in  a  moist  con- 
dition, to  the  volume  which  it  would  occupy  in  a  dry" 
state  at  0°  C.  and  760 % mm.  pressure,  the  following 
formula  is  used :  b  is  the  observed  barometric  press- 
ure, t  the  temperature,  e  the  maximum  tension  of 
aqueous  vapour  at  this  temperature,  and  V  the 
observed  volume :  — 

V =  V  b~e 

760(1+0.003670* 

In  very  exact  work  corrections  should  also  be  in- 
troduced for  the  expansion  of  the  mercury  and  glass 
of  the  barometer. 

Only  those  volumes  can  be.  directly  compared  with 
one  another  that  have  been  reduced  to  equal  pressure 
and  temperature,  the  tension  of  the  liquid  being  also 
allowed  for. 

Parallel  gas  measurement  can  be  carried  on  under — 

1.  Varying   pressure,   varying   temperature,   and 
varying  volume. 

2.  Constant  pressure,  constant  temperature,  and 
varying  volume. 

3.  Constant  temperature,  varying  pressure,  and 
constant  volume. 

4.  Constant   pressure,  varying   temperature,  and 
varying  volume. 

In  the  first  case  the  gas  volumes  found  must  be 
reduced  to  like  temperature  and  pressure.  In  the 
second  and  third  the  resulting  volumes  can  be 
directly  compared,  since  density  and  pressure  are 
directly  proportional. 


CHAPTER   III 

APPARATUS  FOR  GAS  ANALYSIS  WITH  WATER 
AS   THE  CONFINING  LIQUID 

A.    GAS  BURETTES 
1.    The  Simple  Gas  Burette  (Fig.  27) 

THIS  consists  of  two  glass  tubes,  A  and  B,  which 
are  set  in  iron  feet  and  are  connected  by  a  thin  rub- 
ber tube  about  120  cm.  long.  To  facilitate  the  clean- 
ing of  the  burette  the  rubber  tube  is  divided  in  the 
middle  and  the  two  ends  joined  by  a  piece  of  glass 
tubing. 

Inside  the  feet  the  tubes  A  and  B  are  bent  at  right 
angles  and  conically  drawn  out.  The  end  projecting 
from  the  iron  is  of  about  4  mm.  external  diameter 
and  is  somewhat  corrugated,  so  that  a  rubber  tube 
may  be  tightly  fastened  to  it  by  wire  ligatures. 

The  measuring  tube  A  ends  at  the  top  in  a  capil- 
lary tube  C  of  from  J  to  1  mm.  internal  diameter 
and  about  3  cm.  long.  Over  this  a  short  piece  of 
new  black  rubber  tubing  is  wired  on.  The  rubber 
tube  is  closed,  in  a  completely  satisfactory  manner,  by 
a  Mohr  pinchcock  which  is  put  on  close  to  the  end  of 
the  capillary.  The  author  at  first  closed  the  burette 
with  a  glass  stopcock,  but  experience  has  shown  it  to 
be  much  easier  to  make  tight  connections  with  rubber 

34 


CHAP,  in        APPARATUS   FOR   GAS   ANALYSIS 


tubing  and  pinchcocks  than  it  is  to  obtain  perfectly 
tight    glass    stopcocks.      Moreover,    the 
absence  of   glass   stopcocks   renders   the 
apparatus  less  fragile  and  less  costly. 

Further,    as   will    be    seen    from    the 
description    of    the    complete    analysis, 
the  rubber  connections    do   not   usually 
come    in    contact    with    the    absorbent, 
and    if    they   do,  the  amount  of  the  ab- 
sorbent is  so  very  small  that  there  is  lit- 
tle   danger   that   the 
rubber    will    become 
slippery  and  slide  off 
from  the    glass  tube. 
The     author     would 
here  call  especial  at- 
tention   to    the    fact 
that,    whether     glass 
stopcocks    or     pieces 
of  rubber  tubing  are 
used,  they  must  with- 
out fail  be  tested  from 
time  to  time  to  see  if 
they  are  tight.     The 
pinchcock    is    always 
taken    off   from    the 
rubber     tube    after 
using,     this     helping 
much    to     keep     the 
latter  in  good  condi- 
tion.     Notwithstand-  FlG  2r. 
ing     the      fact     that 
readings  cannot  be   made   under  the   rubber   tube. 


36  GAS  ANALYSIS  PARTI 

and  that  the  pinchcock  cannot  always  be  put  on 
above  the  tube  in  exactly  the  same  position,  no 
error  results  therefrom,  since  the  internal  diameter 
of  the  glass  tube  C  is  very  small.  The  author 
has  found  that  the  differences  in  volume  are  much 
less  than  a  tenth  of  a  cubic  centimeter,  a  varia- 
tion which,  in  determinations  not  made  over  mer- 
cury, may  be  entirely  disregarded.  The  graduated 
measuring  tube  A  contains  100  ccm.,  the  lowest 
mark  being  slightly  above  the  iron  foot.  The 
cubic  centimeters  are  divided  into  fifths,  and  the 
numbers  run  both  up  and  down.  The  tube  .Z?, 
which  we  will  call  the  level-tube,  is  somewhat 
widened  at  the  upper  end  to  facilitate  the  pouring 
in  of  liquids. 

With  the  simple  gas  burette  alone  an  analysis  may 
be  made  of  a  gas  mixture  not  too  soluble  in  water, 
and  the  author  used  it  with  good  success  before 
devising  the  apparatus  to  be  mentioned  later.  For 
these  reasons  the  manipulation  by  means  of  which  it 
is  possible  to  carry  out  an  analysis  with  this  simplest 
form  of  burette  will  be  described. 


MANIPULATION  OF  THE  GAS  BURETTE 

Fill  the  tubes  A  and  B  with  water,  taking  care  to 
drive  all  air  out  of  the  connecting  rubber  tube  by 
suitably  raising  or  lowering  the  tubes  ;  then  join  the 
burette  to  the  vessel  containing  the  gas  by  means  of 
a  glass  or  rubber  tube  filled  with  water.  (This  con- 
necting tube  can  easily  be  filled  with  water  by  rais- 
ing the  level-tube.) 

To  fill  the  burette  with  the  gas  to  be  examined, 


CHAP,  in        APPARATUS   FOR   GAS  ANALYSIS  37 

grasp  the  tube  B  in  the  left  hand,  close  the  rubber 
tube  at  D  by  pressing  it  between  the  little  finger  and 
the  palm  of  the  hand,  and  pour  out  the  water  in  B. 

Place  the  level-tube  on  the  floor  and  open  the  pinch- 
cock  E.  The  water  will  now  flow  into  the  level-tube 
and  the  gas  will  be  drawn  into  the  burette.  When 
A  is  filled  with  the  gas,  close  the  pinchcock  E,  discon- 
nect A  from  the  gas-holder,  and  after  the  liquid  has 
run  down  from  the  walls  of  the  burette,  take  up  the 
tubes  by  the  iron  feet  and  by  raising  or  lowering 
bring  the  water  in  the  tubes  to  the  same  level.  The 
gas  is  now  under  atmospheric  pressure,  and  its  vol- 
ume is  read  off. 

To  measure  off  exactly  100  ccm.,  bring  somewhat 
more  than  100  ccm.  of  the  gas  into  the  burette,  close 
the  latter  with  the  pinchcock,  and  let  the  water  run 
down.  Now  compress  the  gas  to  less  than  100  ccm. 
by  raising  the  level-tube,  close  the  rubber  tube  at  6r 
with  the  thumb  and  first  finger  of  the  left  hand,  set 
the  level-tube  on  the  table,  and  raising  the  burette 
in  the  right  hand  to  the  level  of  the  eyes,  carefully 
open  the  rubber  tube  and  let  the  water  run  back 
until  the  meniscus  stands  at  the  100  ccm.  mark. 
Keeping  the  rubber  tube  still  compressed,  open  the 
pinchcock  for  a  moment ;  the  excess  of  gas  will 
escape,  and  there  remains  in  the  burette  exactly 
100  ccm.  of  gas  under  atmospheric  pressure. 

To  bring  as  much  as  possible  of  the  absorbent  into 
the  burette,  lower  the  level-tube  until  the  expanded 
gas  begins  to  enter  the  rubber  tube,  compress  the 
tube  at  D  as  before  described,  and  pour  the  water 
out  of  B.  The  absorbing  liquid  is  now  poured  into 
#,  and  the  tube  raised  as  far  as  the  rubber  tube 


GAS   ANALYSIS  PART  i 

permits  ;  in  this  way  a  considerable  amount  of  the 
reagent,  diluted  with  the  water  in  the  rubber  tube,  is 
brought  into  the  burette. 

Compressing  the  tube  at  (7,  bring  the  gas  into 
thorough  contact  with  the  absorbent  by  vigorously 
shaking  the  burette.  When  no  further  decrease  of 
the  volume  of  the  enclosed  gas  takes  place,  the  read- 
ing is  made  as  before  described.  The  difference  in 
volume  gives  the  amount  of  the  absorbed  gas. 

The  advantages  of  this  simple  burette  over  the 
other  similar  forms  with  which  the  author  is  ac- 
quainted, are  the  following  :  — . 

1.  Easier  and    quicker   manipulation,  since   both 
tubes  may  be  freely  moved,  and  since  the  adjusting 
of   the  levels  does  not    take    place  through  narrow 
stopcocks,  but  on  the  contrary  can  be  instantly  done 
by  raising  or  lowering  the  tube. 

2.  The  possibility  of  bringing  the  gas  under  very 
different  pressures  by  raising  or  lowering  one  of  the 
tubes,  thus  rendering  it  easy,  from  the  beginning  of 
the  analysis,  to  bring  the  gas  into  contact  with  large 
amounts  of  the  absorbent. 

3.  The   simple    glass   tubes   can   be   more  easily 
cleaned,  are  less  liable  to  be  broken,  and  are  cheaper. 

In  the  analysis  of  gases  which  are  very  soluble  in 
water  (among  these  may  be  classed  carbon  dioxide 
except  when  it  is  present  in  very  small  amounts,  as  is 
the  case  in  illuminating  gas  and  some  furnace  gases), 
the  measurement  of  the  initial  volume  cannot  be 
made  over  water,  nor  over  water  saturated  with  the 
gases.  In  this  case  one  must  use  a  gas  burette  which, 
since  it  is  a  modification  of  the  Winkler  apparatus, 
we  will  call  the  modified  Winkler  gas  burette, 


CHAP,  in        APPARATUS   FOR   GAS   ANALYSIS 


2.  The  Modified  Winkler  Gas 
Burette  (Fig.  28) 


This  consists  of  the 
level-tube  a  and  the 
measuring  tube  b  con- 
nected by  a  thin  rub- 
ber tube  about  120  cm. 
long  and  fastened  into 
iron  feet,  b  is  a  glass 
tube  of  about  100  ccm. 
capacity,  provided  with 
the  three-way  cock  c 
and  the  simple  glass 
stopcock  d.  The  space 
between  the  two  stop- 
cocks is  divided  into 
exactly  100  equal  parts, 
and  each  part  into  fifths. 
The  thick-walled  tube  e 
must  have  an  internal 
diameter  of  from  only 
|  to  1  mm.,  so  that 
bubbles  of  the  gases 
which  are  passed  in 
and  out  cannot  stop 
in  the  tube. 

Instead  of  the  glass 
stopcock  d  a  rubber 
tube  and  pinchcock 
may  be  used  as  with 
the  simple  burette. 


FI&.  28. 


40  GAS  ANALYSIS  PART  i 

Before  filling  the  burette  with  the  easily  soluble 
gases,  the  tube  b  is  first  dried  by  rinsing  it  out  with  a 
few  cubic  centimeters  of  absolute  alcohol  and  then 
with  ether,  the  latter  being  driven  out  by  aspirating 
through  the  tube  the  gas  to  be  analysed.  To  do  this, 
join  the  end  e  of  the  burette  by  means  of  a  rubber 
tube,  or  better  a  glass  tube,  to  the  vessel  containing 
the  gas  and  bring  the  three-way  cock  into  such  a 
position  that  its  longitudinal  opening  communicates 
with  the  inside  of  the  burette.  Connect  the  cock 
with  the  aspirator.  After  the  gas  has  been  drawn 
through  for  a  time,  close  the  lower  and  the  upper 
stopcocks.  The  gas,  if  under  pressure,  is  brought  to 
atmospheric  pressure  by  momentarily  opening  the 
upper  stopcock.  The  remainder  of  the  apparatus  is 
now  filled  with  water  run  in  through  the  three-way 
cock,  which  is  so  turned  that  it  communicates  with 
the  rubber  tube.  The  water  must  previously  be 
saturated  with  those  constituents  of  the  gas  mixture 
which  are  slightly  soluble  in  water.  If  the  mixture 
contains  very  soluble  gases,  a  and  b  are  connected  by 
bringing  o  into  the  proper  position,  and  the  gases  are 
absorbed  directly  in  the  burette  by  shaking  them 
with  the  water  therein.  When  a  mixture  contains 
easily  soluble  gases,  they  may  be  absorbed  with  water 
and  then  determined  in  the  solution  by  titration.  In 
the  analysis  of  very  soluble  gases,  it  is  preferable, 
except  in  a  few  rare  cases,  to  lead  large  quantities  of 
the  gas  mixture  through  suitable  apparatus  contain- 
ing known  amounts  of  the  absorbents,  and  to  deter- 
mine the  quantity  of  the  unused  reagent  by  titration. 

The  absorbing  liquids  for  determining  the  con- 
stituents which  are  only  slightly  soluble  in 'water, 


CHAP,  in        APPARATUS  FOR   GAS  ANALYSIS 


41 


are  brought  into  the  burette  by  means  of  a  funnel 
connected  with  the  longitudinal  opening  of  the  stop- 
cock by  a  piece  of  rubber  tubing. 
Beyond  this  the  manipulation 
is  the  same  as  with  the  simple 
gas  burette. 

3.  The  Honigmann  Gras  Burette 

The  burette  A  (Fig.  29)  con- 
tains 100  ccm.  divided  into  ^ 
com.,  the  zero  point  being  at  the 
lower  end  of  the  burette.  At 
the.  top  it  is  closed  by  a  glass 
stopcock  and  the  lower  end  be- 
low the  graduations  is  drawn 
out  to  smaller  diameter  to  per- 
mit of  a  piece  of  rubber  tubing 
being  easily  slipped  over  it.  The 
absorption  liquid  is  placed  in  a 
glass  cylinder  e,  which  should  be 
tall  enough  to  allow  the  burette 
to  be  lowered  to  any  desired 
point  into  the  liquid.  The 
Honigmann  gas  burette  is  suited 
only  to  the  rapid  and  approxi- 
mate determination  of  carbon 
dioxide  in  gas  mixtures  which 
contain  fairly  high  percentages 
of  this  constituent.  In  making 
a  determination,  the  burette  is 
first  thoroughly  cleaned  and  dried,  and  the  gas  to 
be  analysed  is  then  passed  through  it  until  all  air  in 


FIG.  29. 


42  GAS   ANALYSIS  PART  i 

the  burette  has  been  displaced.  Stopcock  a  is  now 
closed  and  the  rubber  tube  is  immersed  in  a  solution 
of  potassium  hydroxide  in  the  manner  shown  in 
the  figure.  The  solution  of  potassium  hydroxide 
is  made  by  dissolving  one  part  of  commercial 
potassium  hydroxide  in  two  parts  of  water.  The 
burette  is  lowered  into  this  solution  until  the  liquid 
stands  exactly  at  the  zero  point,  and  the  stopcock  a 
is  then  carefully  opened  until  the  liquid  inside  the 
burette  rises  to  the  same  mark.  The  tube  now  con- 
tains 100  ccm.  of  the  gas  at  atmospheric  pressure. 
The  absorption  of  the  carbon  dioxide  is  effected  by 
grasping  the  burette  between  the  thumb  and  fingers 
in  the  manner  shown  in  the  figure,  and  turning  it 
downward  so  that  the  caustic  potash  will  flow  along 
the  walls  of  the  burette  and  cause  the  absorption  of 
the  carbon  dioxide.  During  this  operation  the  open 
end  of  the  rubber  tube  must,  of  course,  remain  below 
the  surface  of  the  solution  in  the  cylinder.  After 
all  the  carbon  dioxide  has  been  absorbed  the  burette 
is  again  brought  to  a  perpendicular  position  and 
lowered  into  the  liquid  in  the  cylinder  until  the 
liquid  surfaces  on  the  inside  and  outside  of  the 
burette  stand  at  the  same  height.  The  reading  is 
now  taken,  and  the  result  gives  directly  the  per- 
centage amount  of  carbon  dioxide  present  in  the 
original  gas  mixture. 

4.    The  Bunte  Gas  Burette 

This  consists  essentially  of  the  burette  A  and  the 
level-bottle  B  (Fig.  30).  The  burette  is  closed  at 
the  top  by  the  three-way  stopcock  (7,  and  above 


CHAP,  in       APPARATUS   FOR   GAS   ANALYSIS 


43 


this  there  is  the  tube  D,  which  is  provided  with  a 
mark  about  5  cm.  above  the  stopcock.  The  lower 
end  of  the  burette  is 
closed  by  a  simple 
glass  stopcock,  and  is 
connected  with  the 
level-bottle  B  by  a 
long  piece  of  rubber 
tubing.  A  pinchcock 
is  placed  upon  this 
rubber  tube  a  short 
distance  below  the 
end  of  the  burette. 
Inasmuch  as  all  of 
the  readings  with  this 
burette  will  lie  be- 
tween the  zero  point 
and  the  50  ccm.  mark, 
the  instrument  is  made 
shorter,  and  conse- 
quently easier  to  han- 
dle, by  widening  the 
upper  portion.  The 
horizontal  opening  of 
the  stopcock  C  is 
closed  by  a  piece  of 
rubber  tubing  and  a 
pinchcock.  The  bu- 
rette and  level-bottle 
are  supported  on  an 

,       P    .,        ,,  FIG.  80. 

iron  stand  of  the  form 

shown   in  the  figure,  the  burette  being  held  in   a 

spring   clamp  which   permits  of   its   easy  removal 


44  GAS  ANALYSIS  PART  i 

The  calibration  of  the  burette  runs  from  the  zero 
point,  which  is  near  the  lower  end,  up  to  100  ccm. 
at  the  upper  stopcock.  The  calibration  is  carried 
on  below  the  zero  point  for  10  ccm.  There  must 
also  be  provided  a  thick  walled  glass  bottle  /S 
supplied  with  a  one-hole  rubber  stopper  carrying 
a  short  piece  of  glass  tubing  which  is  closed  by 
a  piece  of  rubber  tubing  and  a  screw  pinchcock. 
A  piece  of  glass  tubing  bent  in  the  shape  fl  is 
also  necessary  for  running  water  into  D. 

Manipulation.  —  Fill  the  level -bottle  B  with  water, 
connect  the  rubber  tube  with  the  burette  in  the  man- 
ner shown  in  the  figure,  open  the  pinchcock  H  and 
the  two  stopcocks  of  the  burette,  and  allow  water  to 
rise  in  the  burette  until  D  is  partially  filled.  Close 
G-  and  If.  Now  turn  the  stopcock  C  until  D  com- 
municates with  jP,  and  open  the  pinchcock  on  F 
until  the  bore  of  the  stopcock  and  the  rubber  tube 
are  filled  with  water.  Then  close  the  pinchcock. 
Slip  the  pinchcock  H  up  to  the  lower  end  of  the 
burette.  Close  it,  and  remove  the  long  rubber  tube 
from  the  burette.  Connect  F  with  the  reservoir  con- 
taining the  gas  to  be  analysed,  and  open  the  pinch- 
cock on  F  and  the  lower  glass  stopcock  of  the  burette. 
Place  under  the  burette  a  beaker  to  catch  the  water 
which  runs  out.  The  water  in  the  burette  will  now 
flow  out,  and  the  gas  will  be  drawn  over  into  the 
tube.  Draw  into  the  burette  rather  more  than  100 
ccm.  of  gas. 

The  gas  in  the  burette  is  always  read  at  the  press- 
ure of  the  atmosphere  plus  the  pressure  of  the  column 
of  water  standing  in  D  up  to  the  mark.  For  conven- 
ience in  calculating  results  it  is  desirable  that  the 


CHAP,  in        APPARATUS   FOR   GAS   ANALYSIS  46 

original  volume  be  exactly  100  ccm.  at  this  pressure. 
To  measure  off  this  exact  volume  close  the  stopcock 
(7,  open  the  pinchcock  H  until  the  long  rubber  tube  is 
filled  with  water,  and  then  slip  this  carefully  over  the 
lower  end  of  the  burette,  after  first  making  sure  that 
there  are  no  bubbles  of  gas  in  the  tip  of  the  burette 
below  the  stopcock.  Now  open  H  and  6r,  and  allow 
water  to  rise  nearly  to  the  zero  point.  Close  6r,  and 
then  turn  (7, -so  that  A  communicates  with  D.  Since 
the  gas  in  the  burette  is  under  slight  pressure,  bubbles 
will  escape  up  through  the  water  in  D.  Bring  the 
water  in  D  exactly  to  the  mark,  and  then  by  care- 
fully opening  6r  allow  the  water  in  the  burette  to 
rise  until  it  stands  exactly  at  zero.  There  is  now  in 
the  burette  100  ccm.  of  gas  under  the  pressure  of  the 
atmosphere  plus  the  column  of  water  in  D.  Close  C, 
and  proceed  to  the  absorption  of  the  constituent  of 
the  gas  mixture  which  is  to  be  determined. 

This  absorption  is  brought  about  by  introducing  a 
liquid  absorbent  into, the  burette  through  the  lower 
end.  Since  these  absorbents  for  the  various  gases 
are  usually  concentrated  solutions,  it  is  undesirable 
to  allow  the  absorbent  to  be  diluted  by  the  water  still 
remaining  in  the  burette  between  6r  and  the  zero 
point.  This  water  is  therefore  first  removed  with 
the  aid  of  the  suction  bottle  S.  This  bottle  is  con- 
nected by  means  of  the  rubber  tube  at  its  top  with  a 
water  suction  pump,  and  is  exhausted  of  air.  The 
screw  pinchcock  is  then  closed,  the  long  rubber  tube 
is  slipped  off  from  the  lower  end  of  the  burette,  and 
the  rubber  tube  of  S  is  slipped  over  the  burette  tip. 
The  screw  pinchcock  on  S  is  now  opened,  Gr  is 
then  carefully  turned,  and  the  water  in  the  burette 


46  GAS   ANALYSIS  PART  i 

is  slowly  drawn  off  until  it  has  fallen  to  a  point  just 
above  Gr.  Gr  is  then  closed,  the  pinchcock  of  S  is 
closed,  and  the  suction  bottle  is  detached.  The 
reagent  to  be  introduced  into  the  burette  is  now 
poured  into  a  small  evaporating  dish,  and  this  dish 
is  brought  up  under  the  tip  of  the  burette  ;  G-  is 
carefully  opened,  and  the  liquid  at  once  rises  in  the 
burette.  When  no  more  will  enter,  close  (7,  remove 
the  dish,  grasp  the  burette  with  the  thumb  and  the 
first  two  fingers  of  the  right  hand  at  the  stopcock  (7, 
and  open  the  spring  clamp  with  the  left  hand.  Place 
the  first  and  second  fingers  of  the  left  hand  below  the 
stopcock  6r,  pour  out  the  water  in  Z>,  and  tip  the 
burette  backwards  and  forwards  so  that  the  absorb- 
ing liquid  will  flow  along  its  entire  length.  Place  it 
again  in  the  clamp,  bring  the  dish  of  the  absorbent 
under  the  tip,  and  allow  more  liquid  to  enter  if  it 
will,  repeating  the  tilting  of  the  burette  in  the  man- 
ner just  described.  When  the  absorbent  will  rise  no 
farther  in  the  burette,  that  is,  when  the  absorption 
of  the  gas  is  completed,  place  the  burette  in  the 
clamp  in  such  a  position  that  its  upper  end  is  below 
the  level-bottle  B,  put  a  beaker  under  #,  and  insert 
in  the  end  of  the  rubber  tube  of  B  the  fl -shaped  glass 
tube  already  mentioned.  Hook  this  tube  over  the 
edge  of  D.  Open  the  pinchcock  H  so  that  water 
will  flow  into  Z>,  then  open  (7,  and  lastly  open  Gr. 
Water  will  now  flow  through  the  burette  and  wash 
out  the  absorbent,  and  yet  no  gas  will  escape  during 
the  operation.  When  the  absorbent  has  been  re- 
moved in  this  manner,  close  Gr,  shut  off  the  supply 
of  water  from  B,  and  then  carefully  open  Gr  until  the 
water  in  D  falls  just  to  the  mark.  Read  the  volume 


CHAP,  in        APPARATUS   FOR   GAS  ANALYSIS  47 

of  gas  now  remaining  in  the  burette.  The  differ- 
ence between  this  volume  and  the  original  volume  of 
100  ccm.  will  give  the  per  cent  of  gas  which  has  been 
absorbed. 

Throughout  the  entire  operation  be  sure  not  to 
touch  with  the  hand  any  part  of  the  burette  except 
the  two  stopcocks,  since  otherwise  the  heat  of  the 
hand  would  expand  the  gas  in  the  burette  and  cause 
some  of  it  to  escape  through  the  open  stopcock  Q. 

Determinations  with  the  Bunte  burette  cannot  be 
accurate,  since  the  gas  in  the  burette  is  brought  into 
contact  with  large  volumes  of  water  which  is  un- 
saturated  with  the  gas  mixture,  and  which  will  there- 
fore absorb  some  of  the  gas  of  the  sample.  The 
method  is  also  wasteful  of  reagent,  since  the  reagent 
which  has  once  been  employed  cannot  be  used  over 
again  because  of  its  dilution  by  the  wash  water. 
The  use  of  the  burette  is  limited  to  the  approximate 
determination  of  carbon  dioxide  and  oxygen. 

B.   ABSORPTION  PIPETTES 

On  account  of  the  solubility  of  gases  in  water  the 
accuracy  of  the  analysis  made  by  direct  absorption  in 
a  gas  burette  is  not  very  great,  and  the  applicability 
of  the  method  is  also  limited  by  the  fact  that  only 
those  absorbents  which  do  not  rapidly  attack  rubber 
can  be  used.  Further,  the  apparatus  must  be  cleaned 
after  each  analysis,  and  the  absorbing  liquid  must 
be  frequently  renewed. 

These  disadvantages  disappear  when  the  absorption 
is  made  in  a  special  apparatus  —  the  gas  pipette  — 
as  first  suggested  by  Doyere.  These  gas  pipettes  con- 


48 


GAS  ANALYSIS 


tain  the  reagents,  and  their  construction  renders  it 
possible  to  bring  the  gases  into  intimate  contact  with 
the  absorbents.  There  must  be  as  many  of  them  as 
there  are  absorbable  constituents  in  the  gas  mixture. 
The  following  forms,  varied  to  suit  the  nature  of 
the  different  reagents,  are  used:  — 

1.    The  Simple  Absorption  Pipette 

This  is  a  modification  of  the  Ettling  gas  pipette, 
first  used  by  Doyere  for  the  absorption  of  gases,  and 
it  is  filled  with  such  absorbing  liquids  as  rapidly 

attack  rubber,  e.g. 
fuming  sulphuric 
acid,  bromine,  fum- 
ing nitric  acid,  etc. 
(see  Part  II). 

It  consists  of 
two  large  bulbs,  a 
and  b  (Fig.  31), 
joined  by  the  tube 
d,  and  of  a  capil- 
lary glass  tube  <?, 
of  J  to  1  mm. 
internal  diameter, 
and  bent  as  shown 
in  the  figure. 

The  bulb  a  holds 
about  100  ccm., 
and  b  about  150 

ccm.,  so  that  when  100  ccm.  of  gas  is  brought  into  6, 
sufficient  space  for  the  absorbing  liquid  will  remain. 
To  protect  the  pipette  from  being  broken  and  to 


CHAP,  in        APPARATUS   FOR   GAS   ANALYSIS 


49 


facilitate  its  manipulation,  it  is  fastened  to  a  wooden 
or  iron  standard. 

An  iron  standard  of  the  form  shown  in  the  figure 
is  preferable  to  wood,  first,  because  of  its  weight,  and 
second,  because  it  cannot  warp  out  of  shape ;  and  the 
iron  standard  with  a  four-sided  base  is  better  than 
such  a  one  as  is  shown  in  Fig.  37,  because  with  the 
latter  form  there  is  danger  that  one  leg  of  the  pipette 
may  be  pushed  over  the  edge  of  the  table  and  the 
apparatus  fall  and  be  broken. 

On  account  of  the  different  behaviour  of  wood  and 
glass  toward  changes  of  temperature  and  atmospheric 
moisture,  it  is  advisable  to  fasten  the  glass  at  only 
three  places  by  means  of  metal  bands  and  plaster  of 
Paris,  the  capillary  tube  being  allowed  to  project 
from  2  to  3  cm.  above  the  frame.  . 

A  short  piece  of  rubber  tubing  is  wired  on  to  the 
free  end  of  the  capillary.  The  distance  h  must  be 
greater  than  #,  so  that  it  may 
be  possible  to  enclose  a  gas 
between  two  columns  of  liquid 
in  the  pipette. 

2.  The  Simple  Absorption  Pip- 
ette for  Solid  and  Liquid 
Reagents 

The  only  difference  between 
this  and  the  simple  pipette  is 
that  in  place  of  the  bulb  b  there 
is  inserted  the  cylindrical  part 
C  (Fig.  32),  which  can  be  filled 
with  solid  substances  through  the  neck  i. 


FIG.  32. 


A  cork  or 


50  GAS   ANALYSIS  PARTI 

rubber  stopper,  held  in  place  by  a  wire,  closes  the 
neck  i. 

A  glass  tube  closed  at  the  top,  and  over  which  a 
rubber  ring,  cut  from  a  rubber  tube,  is  drawn,  also 
makes  a  good  stopper.  By  this  arrangement  only 
a  narrow  strip  of  rubber  is  exposed  to  the  action  of 
the  reagent. 

DOUBLE  ABSORPTION  PIPETTES 

Reagents  which  are  acted  upon  by  oxygen,  i.e. 
alkaline  pyrogallol,  cuprous  chloride,  ferrous  salts, 
etc.,  cannot  of  course  be  kept  in  the  above  form  of 
pipette,  since  the  reagent  in  a  would  become  inactive 
in  a  short  time  through  contact  with  the  air.  The 
author  sought  to  avoid  this  difficulty  by  protecting 
the  reagent  with  a  layer  of  high-boiling  petroleum, 
after  first  convincing  himself  that  the  tension  of 
the  petroleum,  resulting  from  its  solubility  in  the 
reagent,  did  not  cause  a  perceptible  error.  It  was 
soon  found,  however,  that  although  such  hydro- 
carbons lessen  decidedly  the  access  of  air,  they 
do  not  by  any  means  form  a  perfect  protection. 
Further  experiment  on  this  subject  led  to  the 
construction  of  — 

3.    The  Double  Absorption  Pipette  (Fig.  33) 

This  pipette  permits  the  use  of  the  reagents  in 
question  under  an  easily  movable  atmosphere  which 
is  free  from  oxygen,  and  the  reagent  employed  may 
be  kept  completely  saturate^,  with  those  constituents 
of  the  gas  that  it  does  not  strongly  absorb,  this  being 
a  great  advantage.  The  pipette  consists  of  the  large 


CHAP,  in       APPARATUS  FOB   GAS  ANALYSIS 


51 


glass  bulb  #,  of  about  150  ccm.  capacity,  and  three 
smaller  bulbs,  5,  <?,  and  c?,  each  containing  only  100 


FIG.  33. 


ccm.     They  are  connected  by  the  bent  tubes,  0,  /, 
and  </,  and  end  in  the  bent  capillary  tube  k. 

The  pipette  is  fastened  to  a  wooden  or  iron  stand- 
ard in  the  manner  already  described  (see  p.  49). 

4.    The  Double  Absorption  Pipette  for  Solid  and 
Liquid  Reagents  (Fig.   34) 

The  construction  may  be  easily  understood  from 
the  figure  and  from  what  has  already  been  said. 

To  prepare  the  double  pipettes  for  use,  introduce 
the  solid  substance  to  be  employed,  and  then  fill  the 
pipette  completely  with  the  gas  to  be  analysed  by 


GAS   ANALYSIS 


PART  1 


slowly  drawing  the  gas  through.  Now  pour  some 
water  through  m  into  the  bulb  d  until  g  is  full. 
Close  the  rubber  tube  I  with  a  pinchcock,  insert 
into  it  a  thin  glass  tube  at  least  one  meter  long, 
and  fasten  a  funnel  to  the  upper  end  of  the  latter 
by  means  of  a  piece  of  rubber  tubing. 


FIG.  34. 


Upon  pouring  the  reagent  into  the  funnel,  the 
pressure  given  to  it  by  the  long  tube  enables  it  to 
quickly  pass  through  the  capillary  tube  k  into  the 
bulb  or  cylinder  a.  This  can  be  still  further 
hastened  by  gentle  suction  at  m. 

After  about  100  ccm.  of  the  reagent  have  been 
introduced,  the  bulb  d  is  nearly  filled  with  water, 
and  the  gas  remaining  in  a  is  driven  out  through 


CHAP,  in        APPARATUS  FOR    GAS  ANALYSIS  53 

the  long  tube  by  blowing  into  m.  The  pipette  is 
now  closed  at  /,  and  shaken  for  some  time  to  remove 
from  the  bulb  b  the  gases  absorbable  by  the  reagent. 
After  any  gas  bubbles  which  may  now  be  in  a  have 
been  driven  out,  suction  is  applied  at  m,  and  so  much 
gas  is  sucked  out  of  the  bulb  b  that  the  liquid  in  d 
will  enter  and  completely  fill  c.  If  the  water  first 
poured  in  is  not  sufficient,  more  must  be  added  from 
time  to  time. 

In  pipettes  thus  prepared  the  tubes  Tc  and  e  and 
the  bulb  a  are  filled  with  the  absorbent,  the  space 
from  b  to  f  with  a  gas  free  from  oxygen,  c  and  g 
with  water,  and  d  with  air  (Fig.  33).  While  the 
reagent  in  the  simple  pipette  may  be  considered  to 
be  saturated  with  gas  only  when  it  is  kept  in  con- 
tinual use,  that  in  the  double  pipette,  on  the  con- 
trary, remains  saturated  for  an  exceptionally  long 
time,  since  the  diffusion  must  take  place  through  the 
confining  100  com.  of  water  and  through  the  narrow 
tube  g.  The  error  caused  by  this  theoretical  possi- 
bility may  be  wholly  disregarded  in  using  the  pipette. 

MANIPULATION  OF  THE  ABSORPTION  PIPETTES 

To  analyse  a  gas  with  the  apparatus  described,  the 
burette  is  filled  with  distilled  water  which  has  been 
previously  saturated,  by  shaking,  with  the  gas  in 
question. 

If  simple  pipettes  are  used,  these  are  so  filled  with 
the  absorbent  that  the  bulb  a  (Fig.  31)  remains  empty. 
The  absorbent  also  must  be  saturated,  by  shaking, 
with  the  gases  which  are  but  slightly  soluble  in  it. 

The  saturating  of  liquids  is  best  done  in  a  flask 


64  GAS   ANALYSIS  PART  i 

half  filled  with  the  same,  a  rapid  stream  of  gas  being 
led  through  the  liquid,  and  the  flask  vigorously 
shaken. 

In  technical  work,  where  the  same  analyses  are 
repeatedly  made,  the  absorbent  is  kept  saturated 
through  continual  use. 

If  the  pipettes  have  the  temperature  of  the  room,  as 
can  easily  be  ascertained  by  introducing  a  thermom- 
eter at  k  (Fig.  35),  the  analysis  is  begun  by  draw- 
ing the  gas  into  the  measuring  tube  in  the  manner 
already  described.  It  is  convenient  to  take  exactly 
100  com.  (see  p.  37),  so  that  the  results  may  be  read 
off  directly  in  per  cents. 

The  apparatus  is  now  arranged  as  shown  in  the 
figure. 

The  pipette  is  placed  on  the  wooden  stand  Gr, 
which  has  the  form  shown  in  the  figure.  The  left- 
hand  end  of  the  base  is  cut  off  to  permit  of  the 
burette  being  pushed  up  close  to  the  end  of  the  top 
of  the  stand. 

The  pipette  is  now  connected  with  the  burette  by 
the  capillary  tube  F,  which  is  a  piece  of  thermometer 
tubing  of*  about  0.5  mm.  internal  diameter.  To  do 
this,  insert  F  in  the  rubber  tube  w,  slip  a  piece  of 
rubber  tubing  about  two  feet  long  over  the  end 
of  &,  and  then,  holding  F  in  the  fingers  of  the  right 
hand  and  pressing  the  rubber  tube  d  between  the 
thumb  and  the  first  two  fingers  of  the  left  hand, 
blow  through  the  rubber  tube  on  k  until  the  liquid 
in  the  pipette  rises  to  about  the  middle  of  the  capil- 
lary F.  Then  insert  the  end  of  the  capillary  in  d. 
If  this  is  properly  done,  the  air  enclosed  in  the  capil- 
lary should  not  occupy  more  than  5  to  10  mm.  of  its 


CHAP,  in       APPARATUS   FOR   GAS   ANALYSIS 


55 


length  and  the  volume  may  then  be  disregarded, 
since  the  error  arising  therefrom  is  about  0.03  ccm. 
If,  however,  a  greater  air  volume  appears  in  the 


FIG.  35. 


66  GAS  ANALYSIS 


PART  I 


capillary  tube,  F  should  be  slipped  out  of  d  and  the 
operation  repeated.  In  certain  cases  the  reagent 
should  not  be  allowed  to  come  into  contact  with  the 
rubber  tube  at  m.  Under  such  circumstances  the 
liquid  is  forced  into  the  capillary  of  the  pipette  until 
it  stands  just  below  the  top  of  the  iron  frame,  and 
the  correction  for  the  very  small  amount  of  air  then 
introduced  can  easily  be  made  if  necessary.  When 
the  pipette  and  burette  have  thus  been  connected, 
the  pinchcock  below  d  is  opened  and  the  level-tube 
a  is  slowly  raised.  The  gas  is  thus  driven  over  into 
the  pipette.  Water  is  allowed  to  ,flow  through  the 
capillary  F  and  the  capillary  tube  of  the  pipette  until 
it  just  reaches  the  top  of  the  first  bulb.  The  pinch- 
cock  at  d  is  then  closed.  The  gas  is  now  enclosed 
between  two  volumes  of  liquid,  the  absorbent  on  one 
side  and  the  water  in  the  capillary  on  the  other. 
The  gas  is  allowed  to  stand  in  contact  with  the 
absorbent  until  the  constituent  to  be  removed  has 
been  entirely  absorbed.  The  level-tube  is  then 
grasped  near  the  top  with  the  left  hand  and  brought 
into  a  lower  position  than  that  occupied  by  the 
burette  b.  The  pinchcock  at  d  is  then  opened  and 
the  gas  is  drawn  back  into  the  burette,  the  liquid  in 
the  pipette  being  allowed  to  rise  to  exactly  the  same 
point  at  which  it  originally  stood  in  F.  The  pinch- 
cock at  d  is  then  closed,  F  is  withdrawn  from  c?,  and 
the  reading  of  the  remaining  gas  volume  in  the 
burette  is  made  in  the  manner  above  described.  It 
frequently  happens  that  complete  absorption  of  the 
gas  can  be  accomplished  only  by  shaking  the  pipette 
after  the  gas  has  been  driven  over  into  it.  In  such 
a  case  a  second  pinchcock  is  placed  on  the  rubber 


CHAP,  in        APPARATUS   FOR   GAS   ANALYSIS  5? 

tube  w,  and  after  the  gas  has  been  transferred  to  the 
pipette,  both  d  and  m  are  closed  and  the  right-hand 
end  of  the  capillanr  F  is  withdrawn  from  m.  The 
frame  of  the  pipette  is  now  grasped  in  the  two  hands, 
and  the  absorbent  is  brought  into  intimate  contact 
with  the  gas  by  shaking  the  pipette  gently  backward 
and  forward,  not  up  and  down.  The  capillary  of  the 
pipette  and  the  tube  F  are  still  full  of  water,  and 
when  the  pipette  and  burette  are  again  connected 
and  the  gas  is  drawn  back  into  the  burette  no  air  is 
introduced. 

The  manipulation  of  the  pipettes  filled  with  solid 
absorbents  is  still  simpler,  for  in  this  case  no  shaking 
is  necessary,  because  of  the  large  surface  of  contact 
between  the  solid  and  the  gas.  On  this  account  also 
the  apparatus  need  not  be  disconnected. 

A  separate  pipette  is  used  for  each  absorbent,  and 
aside  from  the  economy  of  reagents,  the  frequent 
cleaning  of  the  apparatus  is  thus  avoided.  An 
especial  advantage  is,  further,  the  complete  assurance 
that  no  loss  can  take  place  through  ill-fitting  glass 
or  rubber  stopcocks  while  the  gas  is  in  the  pipette  or 
when  the  pipette  is  vigorously  shaken,  and  that  with- 
out fear  of  error  due  to  the  taking  up  of  gases  not 
chemically  absorbable,  large  amounts  of  reagent 
may  be  used,  and  the  work  be  thereby  greatly 
shortened.  After  using,  the  pipettes  are  closed  at 
m  with  a  piece  of  glass  rod,  and  at  k  with  a  small 
cork. 

If  the  absorbing  power  of  the  reagent  is  known 
(see  p.  145),  waste  may  be  avoided,  and  with  one  filling 
of  the  pipette  several  hundred  analyses  (the  number 
depending  upon  the  nature  of  the  gases  examined) 


58  GAS  ANALYSIS  PART  i 

may  be  made,  with  certainty  throughout  as  to  the 
efficiency  of  the  absorbent. 

If  the  work  has  not  been  carelessly  done,  the  gas 
burette  stands  ready  for  the  next  analysis.  If,  on  the 
other  hand,  reagents  have  been  allowed  to  enter  the 
burette,  it  must  be  cleaned,  its  simple  construction 
rendering  this  quite  easy. 

Some  gases  are  completely  absorbed  by  leading 
them  over  into  the  pipette,  while  others  must  remain 
in  the  pipette  for  a  certain  length  of  time.  By 
using  a  small  sand-glass,  the  operator  is  enabled  to 
give  his  whole  attention  to  the  analysis  proper, 
without  fear  of  allowing  too  little  or  too  much  time 
to  elapse. 


CHAPTER   IV 

APPARATUS  FOR  EXACT  GAS  ANALYSIS  WITH 
MERCURY  AS  THE  CONFINING  LIQUID 

GENERAL  REMARKS 

ON  account  of  the  solubility  of  gases  in  water  and 
in  the  reagents,  no  great  accuracy  is  attainable,  even 
when  these  liquids  are  saturated  with  the  gas  mixture 
being  analysed.  If  very  accurate  results  are  desired, 
the  apparatus  must  unquestionably  be  filled  with 
mercury.  A  few  years,  ago  it  was  difficult  to  obtain 
glass  stopcocks  which  were  perfectly  tight,  but  the 
manufacture  of  glass  apparatus  has  been  so  greatly 
improved  of  late  that  satisfactory  instruments  can 
now  easily  be  procured.  Complete  certainty  that 
the  apparatus  is  absolutely  tight  can,  however,  be 
obtained  only  by  the  use  of  apparatus  which  con- 
tains no  stopcocks  or  rubber  connections  whatever, 
and  in  which  all  openings  are  closed  by  fusing  the 
glass  tubes  together. 

A.   APPARATUS  WITH  RUBBER  CONNECTIONS  AND 
GLASS  STOPCOCKS 

I.   Gas  Burettes  with  Correction  for  Variations  in 
Temperature  and  Barometric  Pressure 

Pettersson  1  was  the  first  to  show  that  by  means  of 
a  tube  enclosing  a  volume  of  gas  it  is  easy  to  com- 

1  Zeitschrift  fur  analytische  Chemie,  25,  467-484. 
59 


60  GAS  ANALYSIS  PART  i 

pensate  the  error  which  would  result  from  variations 
in  the  pressure  and  temperature  of  the  atmosphere. 
Extreme  accuracy  in  gas  analysis  can  be  obtained  by 
the  use  of  apparatus  filled  with  mercury,  and  provided 
with  such  a  compensating  tube,  the  results  with  such 
an  instrument  being  quite  as  exact  as  those  obtained 
with  the  more  elaborate  apparatus  for  exact  gas 
analysis  described  on  p.  79,  provided  always  that 
the  stopcocks  and  rubber  connections  are  perfectly 
tight.  Three  different  forms  of  gas  apparatus  with 
temperature  and  pressure  correction  are  shown  in 
Fig.  36,  the  measuring  tubes  being  varied  to  accom- 
modate gas  volumes  of  different  sizes.  Figure  36,  I, 
shows  the  apparatus  intended  for  the  measurement 
of  gas  volumes  which  vary  between  0.5  and  100  ccm. 
Figure  36,  II,  may  conveniently  be  used  when  the  gas 
volume  amounts  to  about  150  ccm.  In  Fig.  36,  III, 
is  shown  an  instrument  which  was  specially  con- 
structed for  the  examination  of  gases  evolved  from 
bacteria,  the  gas  volumes  usually  amounting  to  about 
10  ccm. 

The  instruments  consist  of  the  graduated  measur- 
ing tubes  A,  the  correction  tubes  B,  the  manometer 
tubes  F,  and  the  level-bulbs  Gr.  The  measuring 
tubes  and  level-bulbs  are  mounted  in  suitable  iron 
feet.  The  measuring  tubes  and  the  correction  tubes 
stand  in  the  wide  glass  cylinders  (7,  which  are  filled 
with  water  to  insure  that  these  two  tubes  are  at  all 
times  at  the  same  temperature.  The  measuring  tubes 
are  closed  at  the  top  by  a  double  Greiner-Friedrich 
glass  stopcock,  the  construction  of  which  is  shown  in 
Fig.  36,  IV. 

The  correction  tube  B  and  the  manometer  tube  F 


CHAP,  iv    APPARATUS  FOR   EXACT   GAS   ANALYSIS       61 

are  made  from  simple  glass  tubes  fused  together  in 
the  form  shown  in  the  cut.  g  is  a  small  capillary 
tube.  The  manometer  tubes  are  U-shaped,  and  are 
somewhat  widened  at  k  and  i,  these  two  widened 
portions  having  marks  scratched  on  the  glass  at 


FIG.  36,  I-IV. 

exactly  the  same  height.  The  manometer  tube  is 
joined  to  the  measuring  tube  by  means  of  a  piece  of 
rubber  tubing  connecting  the  end  of  the  capillary  I 
with  the  tube  a  of  the  stopcock.  The  reason  for 
making  the  manometer  tube  so  long  lies  in  the  fact 
that  otherwise,  if  the  apparatus  is  carelessly  handled, 


62  GAS  ANALYSIS  PART  i 

the  mercury  might  easily  be  driven  from  the  manom- 
eter tube  into  the  burette  or  the  correction  tube. 
With  the  arrangement  shown  in  the  figure  this  is 
almost  impossible,  since  the  difference  in  pressure 
must  be  more  than  half  an  atmosphere  before  the 
mercury  can  pass  over  into  either  tube.  The  manom- 
eter tube  is  made  completely  from  glass  to  prevent 
the  mercury  being  contaminated  with  the  dirt  from 
the  interior  of  a  rubber  connection.  If  the  burette 
has  become  dirty,  the  manometer  tube  is  removed, 
and  the  rest  of  the  instrument  may  then  be  cleaned 
without  danger  of  any  change  taking  place  in  the 
gas  volume  enclosed  in  the  correction  tube. 

To  prepare  the  apparatus  for  use,  draw  some  dis- 
tilled water  through  the  capillary  g  into  the  correction 
tube  B,  and  also  moisten  the  walls  of  the  measuring 
tube  A  with  a  drop  .or  two  of  water.  Fill  the  level- 
bulb  G-  with  mercury,  and  turn  the  glass  stopcock  to 
the  position  shown  in  Dr  Then  by  raising  the  level- 
bulb  drive  the  mercury  over  into  the  manometer 
tube  until  the  latter  is  filled  up  to  the  marks  on  k 
and  i. 

Before  proceeding  with  the  analysis,  the  volume  of 
the  manometer  tube  from  the  mark  on  k  to  the  point 
a  must  be  ascertained.  To  do  this,  draw  over  the 
mercury  in  the  manometer  until  it  reaches  #,  then 
turn  the  stopcock  D  until  it  has  the  position  of  D2, 
and  now  draw  any  desired  volume  of  air  into  the 
burette.  Leaving  the  stopcock  open,  read  off  this 
volume  of  air  on  the  scale  of  the  burette,  the  air  here 
being,  of  course,  under  the  prevailing  pressure  of  the 
atmosphere.  Turn  stopcock  D  so  that  the  burette 
communicates  with  the  manometer  tube,  and  drive 


CHAP,  iv    APPARATUS  FOR  EXACT  GAS  ANALYSIS      63 

the  air  over  into  this  latter  tube  until  the  mercury  in 
it  stands  at  equal  height  in  its  two  branches ;  that  is, 
at  the  marks  on  k  and  i.  The  difference  between 
the  two  readings  on  the  measuring  tube,  provided 
the  tube  g  remains  open,  gives  the  volume  of  the 
manometer  from  the  mark  on  k  up  to  a. 

Correction  tube  B  may  be  used  in  either  of  two 
ways.  We  may  enclose  within  it  an  indeterminate 
amount  of  air  by  simply  fusing  together  the  end  of 
the  tube  g  so  that  the  volume  in  the  correction  tube 
will  correspond  to  the  barometric  temperature  and 
pressure  prevailing  at  the  time  of  operation,  or  we 
may  fill  B  with  such  an  amount  of  air  that  the 
apparatus  will  indicate  directly  gas  volumes  reduced 
to  standard  conditions, — that  is,  to  0°  C.  and  760  mm. 
pressure.  In  the  latter  case,  the  gas  will  have  at 
the  ordinary  temperature  of  the  room  a  pressure 
somewhat  above  that  of  the  atmosphere.  In  the 
former  case  the  barometer  and  the  thermometer 
must  be  read  at  the  time  the  tube  g  is  fused  to- 
gether, so  that  we  may  be  able  to  correct  gas  vol- 
umes whenever  this  is  necessary. 

In  many  cases  it  is  highly  desirable  to  so  arrange 
the  apparatus  that  the  reading  on  the  measuring  tube 
A  corresponds  directly  to  volumes  at  0°  C.  and  760 
mm.  pressure.  To  accomplish  this  a  piece  of  rubber 
tubing  is  slipped  over  the  end  of  the  capillary  tube 
g  and  fastened  firmly  in  place  by  a  wire  ligature. 
By  lowering  the  level-bulb,  mercury  is  drawn  over 
into  the  manometer  tube  until  it  reaches  the  capil- 
lary Z,  and  the  burette  is  then  allowed  to  stand 
for  two  hours  in  a  room  of  fairly  constant  tem- 
perature. The  stopcock  D  is  then  opened  so  that 


64  GAS  ANALYSIS  PART  i 

the  contents  of  the  burette  are  in  free  communi- 
cation with  the  atmospheric  air.  As  soon  as  one 
is  convinced  that  all  parts  of  the  apparatus  are  at 
the  same  temperature,  the  gas  volume  in  the  burette 
is  read  exactly,  and  the  temperature  and  barometric 
pressure  are  noted.  The  thermometer  and  barometer 
should  stand  in  the  same  room  with  the  apparatus. 
The  stopcock  D  is  closed  and  the  volume  which  the 
gas  would  occupy  at  0°  C.  and  760  mm.  barometric 
pressure  is  now  calculated. 

Example.  —  The  gas  volume  is  97  ccm.,  the  baro- 
metric pressure  753.3  mm.,  and  the  temperature 
8.75°  C.  The  space  from  k  to  a  in  the  manometer 
has  previously  been  determined  and  found  to  be 
1.8  ccm.  The  tension  of  the  water  vapour  at  8.75°  C. 
is  8.4  mm. 

If  b  represents  the  observed  barometric  pressure, 
t  the  temperature,  e  the  tension  of  water  vapour 
at  that  temperature,  and  V  the  observed  volume, 
the  volume  V0  which  the  gas  would  occupy  under 
standard  conditions  may  be  calculated  from  the  fol- 
lowing formula  :  — 


=  V 


760  (1  +  0.003670 

In  the  above  example  this  volume  is  92.1  ccm. 

Since,  however,  in  making  measurements  with  the 
correction  tube  the  gas  fills  the  space  from  k  to 
a,  this  volume  must  be  subtracted  from  the  above 
result  :  — 

92.1  -1.8  =  90.3  ccm. 

In  order  now  to  adjust  the  gas  volume  in  the  cor- 
rection tube  so  that  readings  of  volumes  in  the 


CHAP,  iv    APPARATUS   FOR   EXACT   GAS  ANALYSIS      65 

burette  will  be  reduced  at  once  to  standard  condi- 
tions, the  stopcock  D  is  turned  so  that  the  burette 
communicates  with  the  manometer  tube,  and  the  gas 
volume  in  the  burette  is  compressed  by  raising  the 
level-bulb  Gr  to  the  volume  which  it  has  been  cal- 
culated that  it  would  occupy  at  0°  C.  and  760  mm. 
pressure.  The  mercury  in  the  manometer  tube  is, 
of  course,  forced  out  of  equilibrium  by  this  operation. 
Air  is  now  blown  into  the  correction  tube  through 
the  rubber  tube  at  g  until  the  mercury  stands  at  the 
same  height  in  the  two  branches  of  the  manometer 
tube,  and  the  rubber  tube  is  then  closed  by  means 
of  a  strong  pinchcock  placed  directly  above  the  end 

of  g. 

A  rubber  tube  cannot  remain  tight  for  any  length 
of  time,  and  therefore  the  glass  tube  g  must  be  fused 
together.  This  cannot  be  done  at  once  because  of 
the  high  pressure  of  the  air  in  the  correction  tube, 
lout  the  operation  can  easily  be  performed  by  first 
removing  the  rubber  tube  joining  the  manometer 
tube  with  the  burette  at  a  and  then  placing  the  cor- 
rection tube  B  in  a  freezing  mixture  of  salt  and 
ice,  allowing  it  to  stand  therein  until  the  mercury 
in  the  manometer  shows  that  the  pressure  on  the 
inside  of  the  correction  tube  is  smaller  than  that  of 
the  external  atmosphere.  The  tube  g  can  now  be 
heated  by  means  of  a  blast  lamp  and  drawn  out  and 
fused  together  directly  below  the  rubber  tube  which 
is  upon  it. 

There  is  danger  that  the  glass  tube  g  may  crack 
when  it  is  heated.  This  can  be  avoided  by  painting 
it  with  a  thin  emulsion  of  plaster  of  Paris  stirred 
up  with  water,  leaving  the  place  where  the  tube  is 


66  GAS   ANALYSIS  PARTI 

to  be  drawn  out  uncovered  by  this  coating.  The 
plaster  of  Paris  offers  an  excellent  protection  against 
the  overheating  of  that  part  of  the  glass  tube  which 
it  is  not  desired  to  soften  and  can  afterward  easily 
be  removed  with  the  aid  of  water. 

The  correction  tube,  after  being  thus  adjusted,  is 
again  joined  to  the  burette.  The  readings  of  gas 
volumes  in  the  burette  now  give  directly  the  volumes 
under  standard  conditions,  no  matter  how  great  may 
be  the  variations  of  temperature  and  pressure,  pro- 
vided always  that  in  making  the  measurements  the 
stopcock  is  turned  to  the  position  of  D^  and  the  mer- 
cury in  the  manometer  tube  is  brought  to  the  marks 
k  and  i  by  expanding  or  compressing  the  gas  in  the 
measuring  tube.  The  exact  adjustment  of  the  mer- 
cury in  the  manometer  tube  is  effected  by  raising  or 
lowering  the  level-bulb  Gr  until  the  mercury  stands 
nearly  at  the  marks  k  and  i,  then  closing  the  stop- 
cock n  and  turning  the  screw  o  so  as  to  exert 
greater  or  less  pressure  on  the  piece  of  rubber  tubing 
against  which  it  plays.  This  piece  of  rubber  tubing, 
as  is  shown  in  the  figure,  connects  the  lower  end  of 
the  burette  with  the  stopcock  n.  In  this  manner 
the  surface  of  the  mercury  in  the  two  arms  of  the 
manometer  may  be  brought  exactly  to  the  same 
level.  This  style  of  adjustment  is  original  with 
Pettersson  and  enables  us  to  effect  slight  changes  in 
the  size  of  the  gas  volume  in  a  most  convenient  and 
rapid  manner.  In  all  cases  where  rubber  tubing 
must  withstand  considerable  pressure  it  is  desirable 
to  use  the  so-called  "patent"  rubber  tubing  which,  al- 
though not  quite  as  elastic  as  the  ordinary  kind,  will 
easily  withstand  a  pressure  of  several  atmospheres. 


CHAP,  iv    APPAKATUS   FOR   EXACT   GAS  ANALYSIS      67 

II.    The  Absorption  Pipettes 

On  account  of  the  great  differences  in  pressure 
caused  by  columns  of  mercury  of  only  moderate 
height  it  becomes  necessary  to  give  to  these  absorp- 
tion pipettes,  which  are  partially  filled  with  mer- 
cury, a  form  somewhat  different  from  that  adopted 
for  the  pipettes  containing  aqueous  solutions. 

1.    The  Simple  Mercury  Absorption  Pipette 

This  consists  of  two  bulbs,  a  and  6,  Fig.  37,  joined 
together  by  a  piece  of  patent  rubber  tubing.  The 
bulb  a  has  a  capacity  of  about  110  ccm.,  and  b  a 
capacity  of  from  120  to  150  ccm. 


FIG.  37. 


GAS  ANALYSIS 


PART  I 


2.    The  Simple  Mercury  Absorption  Pipette  for  Solid 
and  Liquid  Reagents 

This  resembles  the  pipette  just  described,  except 
that  the  bulb  5,  Fig.  38,  is  cylindrical  in  form  and 
has  at  its  lower  extremity  a  cylindrical  neck,  z, 


FIG. 


through  which  the  bulb  can  be  filled  with  solid 
substances,  i  is  then  closed  with  a  cork  or  rubber 
stopper  held  in  place  by  a  wire  ligature. 

3.    The  Mercury  Absorption  Pipette  with  Absorption 
Bulb 

This  pipette  has  in  addition  to  the  two  bulbs  a 
and  £,  Fig.  39,  a  third  bulb  c  filled  with  broken  glass 


CHAP,  iv     APPARATUS   FOR   EXACT  GAS   ANALYSIS       69 

or  with  glass  beads.  The  advantage  of  this  small 
bulb  lies  in  the  fact  that  when  the  gas  is  driven  over 
into  the  pipette,  the  reagent  which  the  latter  contains 
clings  to  the  small  pieces  of  glass  in  <?,  and  causes  a 


FIG.  39. 

more  complete  absorption  of  that  constituent  of  the 
gas  mixture  which  is  to  be  removed.  The  pipette 
has,  however,  one  drawback :  with  viscous  reagents 
bubbles  of  gas  are  liable  to  cling  to  the  broken  glass 
in  c. 

The  mercury  pipettes  are  manipulated  in  exactly 
the  same  manner  as  the  pipettes  for  aqueous  solu- 
tions above  described,  except  that  here  only  small 
quantities  of  the  reagent  are  employed,  in  order  to 
reduce  to  a  minimum  the  error  which  is  caused  by 
the  solubility  in  the  reagent  of  those  gases  which  are 
not  directly  absorbed  by  it.  This  error  cau  be  com- 


70  GAS  ANALYSIS  PART  i 

pletely  avoided  by  introducing  into  the  gas  pipette 
an  amount  of  reagent  sufficient  for  two  analyses  of 
the  gas  mixture  in  question.  In  the  first  analysis  the 
reagent  becomes  saturated  with  those  gases  for  which 
it  is  not  an  absorbent,  and  the  error  due  to  solution 
of  the  gases  in  the  reagent  is  thus  completely  avoided 
in  the  second  analysis.  The  reagents  are  introduced 
into  the  gas  pipette  by  means  of  a  small  pipette  in- 
serted in  the  rubber  tube  b. 

If  it  is  desired  to  avoid  completely  the  error  caused 
by  the  introduction  of  the  small  quantity  of  air  when 
the  connecting  capillary  of  the  form  shown  in  Fig.  35 
is  used,  the  gas  pipette  and  gas  burette  may  be  joined 
by  means  of  a  three-way  capillary  in  the  manner 
shown  in  Fig.  40.  With  the  aid  of  the  small  separa- 
tory  funnel,  it  is  possible  to  remove  the  last  trace  of 
air  from  the  capillary  by  simply  driving  the  reagent 
as  far  as  the  bore  of  the  stopcock  before  opening  the 
stopcock  of  the  burette. 

One  of  the  chief  advantages  of  the  apparatus 
described  in  the  foregoing  pages  consists  in  the 
exact  compensation  of  any  variations  in  the  tem- 
perature of  the  room.  In  the  opinion  of  the  author 
the  gas  volumeter  of  Lunge  is  faulty  in  construction 
because  of  the  three  tubes  of  which  it  is  composed. 
The  measuring  tube  and  the  compensation  tube  are 
not  immersed  in  one  and  the  same  column  of  water, 
and  since  air  is  a  poor  conductor  of  heat,  two  tubes 
standing  free  in  the  air  assume  the  same  temperature, 
only  very  slowly.  The  errors  which  result  from 
variations  in  temperature  are  precisely  the  ones  most 
to  be  feared.  The  temperature  of  an  apparatus  may 
easily  be  raised  1°  C.  by  the  heat  from  the  body  of 


CHAP,  iv    APPARATUS  FOR  EXACT   GAS  ANALYSIS       71 


the  experimenter,  and  frequently  this  rise  in  tempera- 
ture is  considerably  more  than  1°  C.  A  gas  expands 
2~fg  of  its  volume  when  its  temperature  rises  1°,  the 
error  thus  caused  being  about  0.3  per  cent,  while  a 
change  in  pressure  of  1  mm.  causes  an  error  of  only 


FIG.  40. 


yl-g-  of  the  volume ;  that  is,  0.13  per  cent.  The  author 
is  therefore  of  the  opinion  that  all  forms  of  measur- 
ing apparatus  which  are  to  be  used  for  rapid,  and  at 
the  same  time  exact  work,  should  unquestionably  be 
provided  with  water  jackets. 

III.    Gas  Evolution  Apparatus 

The  apparatus  devised  by  Scheibler  and  the  azo- 
tometer  original  with  Knoop  were  among  the  first 


72  GAS  ANALYSIS  PART  i 

instruments  which  permitted  of  the  easy  measurement 
of  volumes  'of  gas  set  free  from  a  weighed  amount  of 
the  substance.  The  Scheibler  apparatus  has  been 
materially  improved  by  Finkener,  and  the  azotometer 
by  Wolf,  Dietrich,  G.  Wagner,  and  F.  Soxhlet.  The 
gas  volumeter,  original  with  Lunge,  makes  automatic 
correction  for  variations  in  pressure,  and  has  been 
recommended  for  the  evaluation  of  pyrolusite  and 
chloride  of  lime,  and  the  determination  of  hydrogen 
peroxide  and  potassium  permanganate. 

With  all  of  these  forms  of  apparatus,  the  procedure 
consists  in  setting  free  a  gaseous  constituent  from  a 
weighed  amount  of  the  substance,  and  then  exactly 
measuring  the  volume  of  the  evolved  gas. 

A  most  convenient  and  accurate  azotometer  is  ob- 
tained by  using  a  burette  with  temperature  and 
barometer  correction  in  conjunction  with  a  gas  evo- 
lution apparatus,  as  is  shown  in  Fig.  41.  A  special 
advantage  of  this  apparatus  lies  in  the  fact  that  it 
permits  of  the  direct  reading  of  the  evolved  gas 
under  standard  conditions ;  that  is,  the  gas  in  the 
burette  is  automatically  reduced  to  the  volume  which 
it  would  occupy  at  0°  and  760  mm.  pressure.  In 
Fig.  41  is  shown  the  burette,  already  illustrated  in 
Fig.  36,  II,  but,  of  course,  the  burette  shown  in  Fig. 
36,  I,  can  just  as  well  be  used.  The  gas  evolution 
apparatus  corresponds  to  that  employed  in  the  usual 
form  of  azotometer,  and  consists  of  the  glass  bottle  q 
provided  with  a  perforated  glass  stopper.  A  wide 
glass  tube,  filled  with  pieces  of  broken  glass,  or  with 
glass  beads,  is  inserted  in  the  opening  of  the  stopper, 
and  the  upper  end  of  this  tube  is  connected  with  the 
capillary  b  of  the  stopcock  D  by  means  of  a  piece  of 


CHAP,  iv    APPARATUS  FOR   EXACT   GAS   ANALYSIS       73 

rubber  tubing  of  small  bore.  To  permit  of  simul- 
taneous communication  between  the  bottle  <?,  the 
burette  A  and  the  correction  tube  JB,  the  stopcock 
is  removed  from  the  collar,  and  both  ends  of  the  open- 


FIG.  41. 


ing  are  closed  with  short  rubber  stoppers,  which  are 

held  in  place  by  a  wire  ligature  passed  around  them. 

To  determine  with  the  aid  of  the  apparatus  thus 

arranged  the  amount  of  a  gas  which  is  set  free  when 


74  GAS  ANALYSIS  PART  i 

a  liquid  is  brought  in  contact  with  a  solid  substance, 
a  weighed  amount  of  the  substance  is  placed  in  the 
bottle  <2,  the  liquid  which  is  to  act  upon  the  sub- 
stance is  placed  in  the  tube  0,  and  this  tube  is  then 
carefully  lowered  into  the  bottle.  The  stopper  of 
the  bottle  is  now  inserted  and  is  held  in  place  by 
means  of  a  wire  ligature.  The  bottle  is  lowered 
carefully  into  a  large  beaker  C  filled  with  water  of 
the  temperature  of  the  room,  and  the  initial  volume 
of  the  gas  in  the  burette  is  read  off,  the  mercury  in 
the  two  arms  of  the  manometer  tube  being  of  course 
first  brought  to  the  same  level.  The  bottle  q  is  now 
tipped  so  that  liquid  flows  from  o  upon  the  substance, 
and  the  bottle  is  shaken  until  no  further  change  of 
gas  volume  can  be  noticed  on  the  scale  of  the  burette. 
The  difference  between  the  initial  and  the  final  read- 
ing on  the  burette  gives  the  corrected  volume  of  the 
evolved  gas. 

In  the  determination  of  gases  which  are  set  free  only 
when  the  liquid  is  brought  to  boiling,  an  apparatus 
of  the  form  shown  in  Fig.  42  may  be  employed. 
Figure  42,  IV,  is  the  gas  evolution  apparatus ;  Fig. 
42,  II,  a  burette  with  temperature  and  barometer 
correction.  The  gas  evolution  apparatus  consists 
of  a  flask  R  and  the  condenser  8.  The  flask  has 
a  side  tube  T  which  is  closed  by  means  of  the  tube 
m  provided  with  the  stopcock  n.  The  lower  ends 
of  both  the  condenser  S  and  the  tube  m  are  care- 
fully ground  into  the  tubes  in  which  they  fit.  In 
using  this  apparatus  the  substance  is  placed  in  the 
flask  R,  this  flask  is  then  exhausted  of  air  through 
k  by  means  of  a  water  suction  pump,  and  the  reagent 
is  brought  into  R  by  pouring  it  into  T  and  carefully 


CHAP,  iv    APPARATUS  FOR   EXACT   GAS  ANALYSIS        75 

lifting  the  tube  m.  The  gas  in  question  is  then  set 
free  by  boiling,  and  is  completely  driven  over  into 
the  burette  by  running  in  liquid  from  T.  If  several 
gases  are  simultaneously  evolved,  they  may  be  passed 


FIG.  42. 


into  different  absorption  pipettes  and  the  amount  of 
each  determined. 

(See  the  determination  of  fluorine  in  the  presence  of 
carbon  dioxide,  p.  378 ;  and  of  carbon  in  iron,  p.  459.) 


76  GAS   ANALYSIS  PART  i 

B.   APPARATUS  FOR  EXACT  GAS  ANALYSIS  WITH- 
OUT RUBBER  CONNECTIONS  OR  STOPCOCKS 

Experience  has  shown  that  even  the-  best  glass 
stopcocks  cannot  be  relied  upon  with  certainty  for 
any  considerable  length  of  time,  and  rubber  connec- 
tions will  gradually  allow  small  quantities  of  gas  to 
pass  through  them.  It  is  therefore  apparent  that 
an  apparatus  which  contains  no  stopcocks  or  rubber 
connections  whatever  possesses  decided  advantages 
over  one  in  which  errors  arising  through  leakage 
are  liable  to  occur. 

The  wonderfully  simple  and  exact  gasometric 
methods  devised  by  Bunsen  fulfil  completely  these 
demands,  but  unfortunately  the  rapid  performance 
of  a  large  number  of  exact  analyses'  is  not  possible 
with  his  apparatus. 

The  method  devised  by  Doyere 1  resembles  that  of 
Bunsen,  in  that  the  analysis  is  carried  out  in  glass 
vessels  fused  together,  and  all  ground  joints  and 
rubber  connections  are  avoided :  it  has,  however,  the 
fault  that  great  accuracy  can  be  obtained  only  by  the 
use  of  very  cumbersome  apparatus. 

By  the  introduction  of  a  different  manner  of  meas- 
uring and  a  somewhat  changed  construction  of  the 
necessary  absorption  pipettes,  the  author  has  en- 
deavoured to  improve  the  Doyere  method,  so  that,  in 
its  changed  form,  rapid  and  very  exact  work  may 
be  possible  without  the  use  of  delicate  physical 
instruments. 

Bunsen  measures  the  gases  under  varying  pressure 
and  varying  volume,  and  Doyere  measures  them  under 

.  Chim.'Phys.  [3],  28,  p.  1. 


CHAP,  iv    APPARATUS   FOR  EXACT  GAS   ANALYSIS       77 

constant  pressure  and  varying  volume,  while  in  the 
method  about  to  be  described  the  measurements  are 
made  under  constant  volume  and  varying  pressure. 
Following  Mariotte's  law,  the  values  so  found  bear 
the  same  proportion  to  one  another  as  do  gas  vol- 
umes under  the  same  pressure. 

If  the  gases  are  saturated  with  moisture  when 
measured,  corrections  for  the  tension  of  aqueous 
vapour  are  unnecessary. 

Doyere l  measures  the  gases  in  a  Bunsen  eudiom- 
eter, and  he  avoids  correction  for  pressure  by  join- 
ing the  eudiometer  with  an  iron  holder  having  a 
screw  attachment,  by  means  of  which  the  mercury 
in  the  tube  and  in  the  suitably  formed  trough  may 
be  brought  to  the  same  level.  The  readings  are 
made  with  a  special  telescope  of  great  exactness. 
The  absorptions  are  effected  in  Doyere's  improved 
Ettling  gas  pipette. 

The  manipulation  of  the  pipettes  demands  that  the 
eudiometer  at  some  place  in  the  mercury  trough 
be  brought  wholly  beneath  the  level  of  the  mercury, 
and  further,  that  the  suction  tubes  of  the  pipettes  be 
as  long  as  the  eudiometer.  From  these  two  particu- 
lars it  results  that  when  a  very  deep  trough  is  used, 
the  pipettes  are  very  unwieldy  and  easily  broken,  or 
that  when  a  shorter  eudiometer  is  employed,  a  sharp 
reading  of  the  scale  can  be  made  only  with  the  most 
perfect  instruments,  since  it  must  be  possible  to 
measure  with  exactness  tenths  of  a  millimeter. 

Doyere  states  that  the  measuring  tubes  used  by 
him  have  a  length  of  20  cm.  and  an  internal  diameter 

1  Ann.  Chim.  Phys.  [3],  28,  p.  1.  Fehling's  Handworterbuch 
der  Chemie,  vol.  1,  p.  512. 


78  GAS  ANALYSIS  PART  i 

of  15  mm.  For  large  gas  volumes  he  uses  vessels 
similar  to  those  employed  by  Bunsen  for  this  pur- 
pose, the  lower  part  being  cylindrical  and  graduated, 
and  ending  above  in  a  bulb. 

The  method  here  to  be  described  permits,  by  the 
employment  of  spherical  measuring  vessels,  the  use 
of  a  shallow  mercury  trough  and  of  shorter,  more 
easily  manipulated,  and  less  fragile  gas  pipettes,  and 
a  measurement  more  than  three  times  as  sharp,  since 
with  this  apparatus,  if  the  gas  at  the  beginning  of 
the  analysis  nearly  fills  the  bulb  at  atmospheric  press- 
ure, the  scale  has  an  available  length  of  760  mm. 
while  Doyere's  measuring  tube  is  only  200  mm.  long. 

The  measurements  are  made  at  constant  volume, 
varying  temperature,  and  varying  pressure.  This  is 
accomplished  by  placing  the  gas  in  small  glass  bulbs 
which  can  easily  be  brought  into  communication  with 
the  manometer  tube,  by  then  expanding  the  gas  to  a 
certain  volume  by  lowering  a  movable  vessel  filled 
with  mercury,  and  finally  reading  on  the  manometer 
tube  the  pressure  under  which  the  gas  now  stands. 
According  to  Mariotte's  law  the  values  thus  ob- 
tained bear  the  same  proportion  to  one  another  as 
do  gas  volumes  under  the  same  pressure. 

The  corrections  which  are  made  necessary  by  the 
changes  in  temperature  and  in  the  pressure  of  the 
atmosphere  are  ascertained  in  a  simple  manner  by 
the  use  of  a  correction  tube. 

The  absorptions  are  effected  in  gas  pipettes  to  be 
described  later. 

In  the  two  preceding  editions  of  this  book  there 
was  described  an  apparatus  which  was  provided  with 
a  barometer  tube  and  with  which  analyses  could  be 


CHAP,  iv     APPARATUS   FOB   EXACT   GAS   ANALYSIS       79 

made  without  the  introduction  of  any  correction 
whatever,  provided  the  whole  apparatus  were  kept 
at  constant  temperature  by  means  of  running  water. 
The  author  is  now  convinced,  however,  that  with  the 
use  of  a  correction  tube  just  as  accurate  results  can 
be  obtained  as  with  the  more  complicated  apparatus, 
and  he  regards  it  as  in  general  undesirable  to  con- 
struct large  pieces  of  apparatus  wThich  have  many 
connections,  since  in  time  all  rubber  becomes  bad, 
the  iron  parts  of  the  apparatus  rust,  and  the  mercury 
becomes  contaminated.  The  apparatus  should  be  so 
designed  as  to  permit  of  the  easy  removal  and  re- 
placement of  any  of  its  parts.  The  author  therefore 
regards  such  pieces  of  ^apparatus  as  the  different 
forms  of  the  Orsat  as  unpractical,  since  here  a  large 
number  of  absorption  vessels  are  joined  together 
by  means  of  several  complicated  connections. 

DESCRIPTION  OF  THE  APPARATUS  BY  W.  HEMPEL 

The  apparatus  (Fig.  43)  consists  of  an  iron  mer- 
cury trough  A  (on  account  of  the  presence  of  water, 
wood  cannot  be  used,  since  it  would  swell  and  change 
form),  of  a  glass  tube  D  graduated  in  millimeters 
and  from  76  to  80  cm.  long,  and  further,  of  the 
wooden  stand  G-  and  the  water  reservoir  E.  The 
sides  of  the  water  reservoir  E  are  glass  panes,  one  of 
which  e  extends  only  so  deep  into  the  mercury  as  to 
leave  room  to  bring  the  capillary  of  the  pipette  B 
under  it  into  the  measuring  bulb  C. 

By  placing  the  measuring  bulb  upon  the  rubber 
stopper  a  in  the  mercury  trough  it  can  always  be 
brought,  by  means  of  the  holder  /,  into  mercury- 


FIG.  48. 


CHAP,  iv    APPARATUS  FOR  EXACT   GAS  ANALYSIS       81 

tight  connection  with  the  graduated  tube  D.  The 
tube  b  and  the  j_-piece  d  are  made  of  iron.  D  is 
connected  with  an  arm  of  d  by  means  of  a  piece  of 
strong  patent  rubber  tubing,  or  ordinary  rubber  tub- 
ing so  wrapped  as  to  enable  it  to  resist  the  pressure 
of  the  mercury.  A  piece  of  patent  rubber  tubing 
joins  the  other  arm  to  the  movable  level-bulb  H,  but 
between  d  and  m  there  is  introduced  the  Pettersson 
device  for  the  fine  adjustment  of  the  mercury.  (See 
Fig.  36.) 

In  making  the  measurement,  the  measuring  bulb 
O  is  brought  into  the  position  shown  in  Fig.  43,  and 
is  pressed  down  tightly  upon  the  rubber  stopper  a  by 
means  of  the  clamp  /.  Mercury  is  then  drawn  out 
through  d  until  the  meniscus  of  the  mercury  in  the 
measuring  bulb  lies  nearly  tangent  to  the  horizontal 
hair  of  a  magnifying  glass  which  is  fastened  to  the 
apparatus  opposite  I.  This  glass  is  not  shown  in 
the  figure,  m  is  then  closed  and  the  exact  adjust- 
ment of  the  height  of  the  mercury  at  I  is  effected  by 
turning  the  screw  n. 

The  height  of  the  mercury  in  the  manometer  tube 
D  is  now  read  with  a  cathetometer,  and  the  pressure 
of  the  gas  in  the  bulb  is  thus  determined.  After 
first  introducing  corrections  for  variations  in  the 
temperature,  the  pressure  of  the  surrounding  atmos- 
phere is  ascertained  by  means  of  the  correction  tube 
described  011  p.  94  and  shown  in  Fig.  53. 

THE  MEASURING  BULB 

The  measuring  bulb  E  (Fig.  44)  is  fastened  to  the 
iron  holder  g  by  means  of  the  projecting  tubes  r  and 


GAS  ANALYSIS 


PART  I 


s;  r,  which  is  closed  at 
the  top,  is  about  5  mm. 
long  and  s  about  30  mm. 
At  from  5  to  7  mm.  be- 
low the  bulb,  s  is  widened 
into  a  collar  x  by  soft- 
ening the  glass  tube  in 
the  blast-lamp  flame  and 
pressing  it  together.  The 
iron  holder  g  has  at  t  a 
thick  perforated  sheet- 
iron  cap  for  holding  r. 
The  holder  bends  around 
the  bulb  and  is  supplied 
at  the  lower  end  with  the 
perforated  iron  plate  w, 
which  is  bent  at  a  right 
angle,  and  holds  the  pro- 
jection s.  u  may  be  set 
where  desired  by  means 
of  the  screw  v,  to  which 
the  slot  through  which  it 
passes  gives  a  play  of  sev- 
eral millimeters,  s  pro- 
jects 4  to  5  mm.  beyond 
the  plate  u.  The  iron 
collar  y  is  fastened  to  g 
in  such  a  position  that  it 
just  slips  under  the  fork 
/  when  the  holder  and 
bulb  are  placed  over  the 
end  of  the  iron  tube  pass- 
ing through  the  rubber 


FIG.  44. 


CHAP,  iv    APPARATUS   FOR   EXACT   GAS   ANALYSIS       83 

stopper  m,  and  are  firmly  pressed  against  the  rubber. 
The  fork  is  firmly  fastened  to  the  slide  i,  which  can 
be  moved  up  and  down  by  the  screw  h.  By  screw- 
ing the  slide  down,  the  measuring  bulb  can  be  pressed 
against  the  rubber  stopper  and  a  tight  connection 
with  the  barometer  tube  thus  be  obtained.  A  scale 
upon  the  slide  i  and  its  guides  makes  it  possible  to 
bring  the  bulb  at  different  times  into  exactly  the 
same  position  as  regards  the  millimeter  scale  of  the 
barometer. 

The  total  height  of  the  measuring  bulbs  varies 
from  7.5  to  9.5  cm. 

Since  the  walls  of  the  measuring  bulbs  used  by  the 
author  are  only  as  thick  as  those  of  ordinary  bulb 
pipettes,  it  was  thought  possible  that,  in  the  meas- 
urement of  very  small  gas  volumes,  the  volume  of 
the  bulb  might  be  decidedly  changed,  since  under 
such  conditions  it  is  exposed  to  nearly  the  full 
pressure  of  the  atmosphere. 

To  settle  this  question,  the  volume  of  the  bulb, 
first  empty  and  then  filled  with  gas,  was  determined 
in  a  stereometer,  and  it  was  found  that  even  with 
large  bulbs  of  100  ccm.  capacity  no  measurable  differ- 
ence of  volume  could  be  detected ;  hence  even  thin- 
walled  glass  bulbs  may  be  used  without  hesitation  for 
these  measurements. 

Curiously  enough,  it  is  quite  difficult  to  lower  the 
measuring  bulb  through  the  water  in  E  (Fig.  43)  down 
into  the  mercury  below  without  some  water  getting 
into  the  inside  of  the  bulb.  If  this  should  happen, 
exact  reading  would,  of  course,  be  impossible.  The 
operation  can  be  performed,  however,  by  bringing  the 
measuring  bulb  into  two  porcelain  crucibles  placed 


84  GAS   ANALYSIS 


PART  I 


one  within  the  other  in  the  manner  shown  in  Fig.  45, 
and  then  filling  these  two  crucibles  with  mercury. 
When  these  are  lowered  through  the  water  into  the 
mercury  the  larger  crucible  A  is  first  removed,  and 
then  the  crucible  JS  is  lowered  away  from  the  mouth 
of  the  bulb.  The  opening  in  the  bulb  is  now  below 


FIG.  45.  FIG.  46. 

the  surface  of  the  mercury,  and  yet  no  water  has 
entered  it. 

By  means  of  the  instrument  shown  in  Fig.  46  the 
air  may  be  sucked  out  of  the  measuring  bulb,  and  the 
gas  sample  can  then  be  transferred  to  the  bulb  by 
means  of  one  of  the  pipettes  described  below. 

THE  GAS  PIPETTES 

The  gas  pipettes  were  devised  by  Ettling  and  were 
first  used  by  Doyere  as  absorption  vessels  for  gas 
analysis. 

They  consist  of  two  bulbs  a  and  b  (Fig.  47),  of  the 
same  size,  joined  together  by  the  tube  c  and  ending 


CHAP,  iv    APPARATUS  FOR  EXACT   GAS  ANALYSIS       85 


in  the  bent  capillary  tube  d.  A  very  small  bore 
thermometer  tube,  and  not  a  tube  of  1  mm.  bore  as 
Doyere  suggests,  is  used  as  the  capillary,  thus  mak- 
ing it  easy  to  avoid  introducing  absorbent  into  the 
measuring  bulb  or  leaving  of  any  considerable  quan- 
tity of  gas  in  the  pipette. 

Gases  move  rapidly  in  capillary  tubes,  but  liquids, 
especially  concentrated  solutions  of  salts,  move  very 


1 


FIG.  47. 


slowly;  hence  it  is  easily  possible  to  bring  the  gas 
residue  in  the  pipette  to  less  than  y^o  of  a  cubic 
centimeter  without  danger  of  the  absorbent  entering 
the  measuring  bulb.  It  is  almost  impossible  to  do 
this  when  wider  glass  tubes  are  used. 

The  pipettes  must  be  so  made  that  the  distance  a 
(Fig.  47)  is  only  as  large  as  or  smaller  than  fi:  the 


86  GAS  ANALYSIS  PART  i 

capillary  must  be  bent  close  to  the  bulb  b.  The 
pipettes  are  fastened  to  the  wooden  standard  in  such 
a  position  that  the  capillary  d  comes  to  within  a  few 
millimeters  of  the  bottom  of  the  mercury  trough 
when  the  pipette  is  placed  in  the  position  shown  in 
Fig.  43. 

The  bulbs  of  the  pipettes  must  be  considerably 
larger  than  the  volume  of  the  gas  to  be  brought  into 
them.  The  inconvenience  of  carefully  cleaning  the 
pipette  after  the  absorption  is  avoided  by  using  a 
special  pipette  for  each  reagent.  Pipettes  of  very 
different  sizes  are  employed,  the  sizes  depending 
naturally  upon  the  dimensions  of  the  measuring 
bulbs. 

To  bring  a  measured  amount  of  the  absorbent  into 
the  pipette,  which  is  first  filled  with  mercury,  connect 
it  by  means  of  a  piece  of  rubber  tubing  e  (Fig.  48) 
with  the  small  burette  /  containing  the  reagent  and 
supported  by  the  clamp  g.  Open  the  pinchcock  A, 
slip  a  rubber  tube  over  the  burette  at  z,  and  by  suc- 
tion so  exhaust  the  air  in  the  burette  that  any  gas 
remaining  in  the  pipette  will  be  drawn  through  the 
capillary  x  and  through  the  absorbent.  The  pipette 
is  thus  completely  filled  with  mercury.  Stop  the 
suction  as  soon  as  the  mercury  is  visible  above  the 
rubber  e,  put  the  rubber  tube  on  the  pipette  at  Z,  and 
draw  the  mercury  back  to  the  capillary.  Note  the 
height  of  the  absorbent  in  the  burette,  and  then  suck 
the  desired  amount  of  the  same  through  the  capillary 
d  into  the  pipette.  At  the  moment  when  the  neces- 
sary amount  of  reagent  has  passed  over,  bring  a  drop 
of  mercury  into  the  burette  at  i. 

The  amount  of  the  absorbent  introduced  may  be 


CHAP,  iv    APPARATUS  FOR   EXACT   GAS  ANALYSIS       87 

sharply  determined  by  drawing  the  mercury  into  the 
pipette   until   the    reagent   is   again   visible   in   the 


FIG.  48. 


capillary  d,  and  then  noting  the  height  of  the  reagent 
in  the  burette. 


GAS  ANALYSIS 


PART  I 


The  bent  capillary  tube  of  the  pipette  is  cleaned 
and  freed  from  all  traces  of  reagent  by  lowering  the 
tube  into  a  beaker  filled  with  distilled  water,  and 
then  drawing  water  into  the  capillary  and  driving  it 
out  again  by  sucking  and  blowing  on  a  rubber  tube 
attached  to  the  open  end  of  a. 

The  pipette  thus  prepared  for  the  analysis  contains 
mercury  between  v  and  w,  between  w  and  x  the 
absorbent,  and  from  x  to  y  mercury. 

GAS  PIPETTES  FOB  SOLID  ABSORBENTS 

To  bring  the  gases  under  examination  into  contact 

with  solid  absorb- 
ents, the  form  of 
pipette  shown  in 
Fig.  49  is  used. 
In  this  the  tube 
c  has  a  branch 
tube  e  through 
which  solid  sub- 
stances, such  as 
sticks  of  phos- 
phorus, are  intro- 
duced into  the  bulb 
b  ;  e  is  then  closed 
at  /  with  a  cork, 
and  the  pipette  is 
filled  as  usual  with  mercury.  When  a  gas  is  drawn 
in,  the  solid  substances  remain  in  the  bulb  6,  and  so 
come  into  contact  with  the  gas. 


FIG.  49. 


CHAP,  iv    APPARATUS  FOR   EXACT   GAS   ANALYSIS      89 


THE  EXPLOSION  PIPETTE 

Combustions  are  made  in  an  explosion  pipette 
(Fig.  50).  This  has  at /two  platinum  wires  and  at 
g  a  glass  stopcock. 
The  wires  are 
fastened  to  two 
screw-eyes,  to 
which  are  con- 
nected the  wires 
from  the  induction 
apparatus.  To  ex- 
plode a  gas  mix- 
ture, it  is  brought 
into  the  pipette, 
the  stopcock  is 
closed,  and  into 
the  end  of  the 
capillary  at  z  a 
fine  sewing  needle  is  inserted,  which  prevents  the 
mercury  being  thrown  out  of  the  capillary  by  the 
strong  pressure  during  the  explosion. 


FIG.  50. 


THE  ABSORPTION 

The  gas  pipettes  already  described  are  used  for  the 
absorptions,  the  manipulation  being  shown  in  Fig.  51 
and  Fig.  52. 

Figure  51  gives  the  position  in  which  it  is  possible 
to  bring  the  gas  completely  into  the  pipette.  The 
measuring  bulb  is  here  brought  below  the  surface  of 
the  mercury  and  the  gas  is  drawn  into  the  pipette 
by  sucking  with  the  mouth  on  a  rubber  tube  attached 


90  GAS   ANALYSIS  PART  i 

to  m.  The  suction  is  discontinued  at  the  moment 
when  the  mercury  begins  to  flow  from  the  capillary 
into  the  bulb  of  the  pipette. 


FIG.  51. 


The  pipette  then  contains  (see  Fig.  47)  mercury 
from  v  to  w,  absorbent  from  w  to  x,  gas  from  x  to  g, 
and  mercury  from  g  to  2,  so  that  the  pipette,  after  it 


CHAP,  iv     APPARATUS   FOR   EXACT   GAS  ANALYSIS       91 

is  taken  out  of  the  mercury  trough,  may  be  vigorously 
shaken  and  a  rapid  absorption  effected. 


FIG.  52 


To  drive  the  gas  from  the  pipette  back  again  into 
the  measuring  bulb,  the  apparatus  is  brought  into  the 
position  shown  in  Fig.  52. 


92  GAS  ANALYSIS 


PART  1 


In  the  beginning  it  is  necessary  to  blow  into  the 
pipette  at  m  to  set  the  gas  in  motion ;  when  it  has 
once  started,  the  mercury  in  the  measuring  bulb  acts 
with  an  aspirating  effect,  so  that  the  gas  passes  over 
of  itself.  At  the  moment  when  the  absorbent  has 
risen  to  about  1  cm.  from  the  end  of  the  capillary  in 
the  measuring  bulb,  the  capillary  is  lowered  under 
the  mercury,  and  mercury  is  drawn  into  the  capillary 
by  sucking  on  the  rubber  tube  attached  to  m.  In 
this  manner  the  entering  of  reagent  into  the  measur- 
ing bulb  may  be  avoided  with  certainty. 

If  a  gas  thread  about  1  cm.  long  remains  in  the  cap- 
illary, this  corresponds  to  approximately  0.001  ccm. 
of  gas,  since  the  total  35  cm.  length  of  the  capillary 
has  a  volume,  determined  by  weighing  the  mercury 
which  it  holds,  of  0.038  ccm.  Hence  from  this 
source  no  appreciable  error  arises. 

The  analysis  is  made  as  follows  :  — 

Fill  the  carefully  cleaned  and  moistened  measuring 
bulb  with  the  gas  under  examination  by  lowering  the 
bulb  into  the  mercury  in  the  trough,  drawing  out  the  air 
in  it  with  a  gas  pipette,  and  bringing  the  gas  into  the 
bulb  either  by  means  of  a  delivery  tube  brought  under 
the  mouth  of  the  bulb  or  by  means  of  a  gas  pipette. 

The  necessary  measurements,  absorptions,  and  ex- 
plosions now  follow,  their  order  being  determined  by 
the  nature  of  the  gas. 

Since  difficulties  arise  only  in  the  use  of  fuming 
sulphuric  acid  over  mercury,  while  all  other  reagents 
can  easily  be  manipulated  in  the  manner  already  de- 
scribed, the  reader  is  referred  to  the  second  part  of 
the  book  for  descriptions  of  the  absorptions  of  the 
various  gases. 


CHAP,  iv    APPARATUS   FOR   EXACT   GAS   ANALYSIS      93 

The  heavy  hydrocarbons  cannot  be  absorbed  with 
fuming  sulphuric  acid  in  the  manner  described,  be- 
cause, on  bringing  together  the  fuming  acid  and 
mercury,  sulphur  dioxide  is  evolved  even  in  the  cold, 
and  acid  sulphates  are  formed  which,  upon  long 
standing,  separate  as  thick  crusts  and  obstruct  the 
pipette.  Since,  however,  the  gases  which  are  not 
absorbable  by  the  fuming  acid  are  very  insoluble  in 
the  same,  a  pipette  completely  rilled  with  the  acid 
may  be  used,  the  mercury  here  coming  into  contact 
with  the  sulphuric  acid  only  in  the  capillary  tube. 
If  care  be  taken  in  the  manipulation  that  no  mercury 
passes  over  from  the  trough  into  the  pipette,  and  if, 
after  using,  all  mercury  be  removed  from  the  capillary 
by  means  of  a  common  suction  pipette  attached  there- 
to, so  that  sulphuric  acid  alone  remains  in  the  pipette, 
a  stoppage  of  the  capillary,  which,  when  it  has  once 
taken  place,  is  difficult  of  removal,  need  not  be  feared. 

To  protect  the  lungs  from  the  fumes  of  the  sul- 
phuric acid,  a  glass  tube  filled  with  pieces  of  caustic 
potash  is  interposed  between  the  rubber  suction  tube 
and  the  pipette. 

The  gases  being  examined  do  not  here,  as  in  the 
other  absorptions,  come  in  contact  with  but  small 
amounts  of  the  reagent,  hence  the  errors  which  might 
result  from  the  solubility  of  the  gases  that  are  not 
in  an  analytical  sense  absorbable  by  fuming  sulphuric 
acid  could  not  be  disregarded.  To  obtain  an  idea  of 
the  solubility  of  the  gases  in  question,  illuminating 
gas  was  freed  from  the  heavy 1  hydrocarbons  and 
carbon  dioxide  by  absorption,  and  the  residue,  con- 

1  By  "  heavy  "  hydrocarbons  are  meant  those  which  are  absorb- 
able by  fuming  sulphuric  acid. 


94  GAS  ANALYSIS  PART  i 

sisting  of  oxygen,  carbon  monoxide,  hydrogen, 
marsh-gas,  and  nitrogen,  was  brought  in  contact 
with  a  large  quantity  of  fresh  sulphuric  acid. 

The  volume  of  the  residue  was  determined  before 
and  after,  and  it  was  found  that  the  change  in  volume 
could  not  be  measured.  Hence  the  solubility  of  the 
gases  not  absorbable  by  sulphuric  acid  may  be  wholly 
disregarded. 

The  data  of  the  experiment  were  the  following :  — 
About  25  ccm.  of  illuminating  gas  was  allowed  to 
stand  for  some  time  in  contact  with  sulphuric  acid, 
was  then  freed  from  sulphur  dioxide  and  the  fumes 
of  sulphuric  acid  by  caustic  potash,  and  was  measured 
moist.  The  result  was  757.7  mm.  pressure  at  16.8°  C. 
The  gas  was  then  shaken  in  a  pipette  with  fresh  con- 
centrated sulphuric  acid,  and  after  standing  for  two 
hours  it  was  brought  into  the  measuring  bulb  and 
measured  moist.  Result  —  757.7  mm.  at  16.6°  C. 

THE  CORRECTION  TUBE 

This  tube  is  used  to  determine  the  volume  of  gas 
which  must  be  added  to  or  subtracted  from  the 
values  determined  in  the  analyses,  in  order  to  com- 
pensate any  variations  due  to  changes  in  temperature 
or  barometric  pressure. 

The  correction  tube  consists  of  the  glass  tube  A, 
Fig.  53,  the  scale  tube  B,  and  the  adjusting  tube  C. 
To  prepare  the  tube  for  use,  it  is  placed  in  the  mer- 
cury trough  of  the  gas  apparatus.  The  latter  should 
stand  in  a  room  where  the  variations  of  temperature 
are  but  very  slight.  A  very  small  amount  of  water 
is  introduced  into  A  through  5,  which  is  as  yet  open, 


CHAP,  iv    APPARATUS   FOR   EXACT   GAS  ANALYSIS      95 


and  mercury  is  then  poured  in  until  it  stands  at  the 
mark  a  and  at  the  zero  mark  in  the  scale  tube.  The 
sharp  adjustment  of  the  mercury  at  these  heights  is 
effected  by  sliding  up  and  clown  in  the  adjustment 
tube  O  a  glass  rod  D.  The 
rod  is  joined  to  0  by  means 
of  a  short  piece  of  rubber 
tubing  c.  When  the  mercury 
has  been  brought  to  the  points 
mentioned,  the  upper  end  of 
b  is  fused  together  directly 
above  the  water  in  the  mer- 
cury trough  by  means  of  a 
small  blast-lamp  flame.  If 
this  is  carefully  done,  there  is 
no  appreciable  heating  of  the 
air  volume  enclosed  in  A. 

The  prevailing  barometric 
pressure  and  the  temperature 
of  the  water  in  the  mercury 
trough  are  now  noted  so  that 
the  volume  of  air  in  the  ap- 
paratus may  be  calculated.  If 
the  barometric  pressure  changes 
during  the  course  of  the  an- 
alysis, the  influence  which  this 

change  would  have  upon  the  gas  pressure  in  the 
measuring  bulb  may  easily  be  determined  by  placing 
the  correction  tube  in  the  mercury  trough  and  bring- 
ing the  mercury  to  the  mark  a  by  raising  or  lowering 
the  glass  rod  D.  The  reading  on  the  scale  tube  B 
then  gives  the  volume  which  must  be  added  to  or 
subtracted  from  the  values  found  in  the  analysis  in 


FIG.  58. 


96  GAS   ANALYSIS  PART  i 

order  to  obtain  results  which  are  directly  comparable 
with  one  another. 

When  a  constituent  of  the  gas  mixture  is  to  be 
absorbed  with  one  of  the  gas  pipettes,  the  correction 
tube  is  removed  from  the  mercury  trough  and  is 
replaced  therein  before  each  reading. 

Unless  very  accurate  results  are  desired,  it  is  suffi- 
cient to  make  all  readings  with  the  unaided  eye,  for 
if  the  eye  be  brought  only  approximately  to  the 
same  plane  with  the  surface  of  the  mercury  column 
which  is  to  be  read,  the  results  thus  obtained  are 
quite  close  to  the  truth. 

The  accuracy  of  the  analysis  may  easily  be  greatly 
increased  by  using  a  number  of  measuring  bulbs  of 
different  sizes  and  determining  their  volumes  by 
filling  them  with  mercury  and  weighing  the  mer- 
cury. The  gas  to  be  analysed  is  then  first  brought 
into  the  largest  bulb  and  one  or  more  of  its  constitu- 
ents are  determined.  If  the  remaining  volume  now 
amounts  to  only  a  half  or  two-thirds  of  the  original 
volume,  this  residue  is  introduced  into  a  smaller 
measuring  bulb.  This  procedure  permits  of  the 
use  of  the  total  length  of  the  manometer  tube  D 
(Fig.  43)  in  making  the  measurements,  and  con- 
sequently insures  much  greater  accuracy .  in  the 
readings. 


CHAPTER   V 

ARRANGEMENT  AND  FITTINGS  OF  THE 
LABORATORY 

THE  room  for  gas  analysis  should  have  a  northern 
exposure  and  should  have  wide  windows.  The  work- 
ing-table should  run  along  the  outer  wall  so  that  the 
operator  may  face  the  window  and  be  able  to  make 
his  readings  without  being  obliged  to  turn  around 
toward  the  source  of  light.  The  floor  should  be 
mercury-tight,  and  should  slope  slightly  toward  the 
middle,  in  order  that  any  mercury  that  may  be 
spilled  may  easily  be  brought  together  and  taken  up. 
If  the  floor  is  of  wood,  it  may  be  made  mercur}^- 
tight  by  covering  it  with  canvas  or  oilcloth,  but 
this  covering  must  then  be  protected  by  laying  upon 
it  large  sheets  of  cardboard.  The  room  should  fur- 
ther be  provided  with  gas  and  with  running  water 
and  with  a  large  sink.  The  sink  should  have  an  iron 
"  S  "  trap,  and  the  lower  bend  of  this  trap  should  be 
bored,  threaded,  and  provided  with  a  screw  plug  to 
permit  of  the  easy  removal  of  any  mercury  that  may 
collect  in  the  trap. 

There  should  also  be  an  ample  supply  of  water  of 
the  temperature  of  the  room.  It  is  convenient  to 
have  this  water  piped  to  every  working-place.  This 
is  cheaply  accomplished  by  placing  near  the  top  of  the 
room  and  above  the  sink  a  galvanised  iron  tank  con- 
H  97 


98  GAS  ANALYSIS  PART  i 

tainiiig  about  100  liters,  and  running  from  the  lower 
part  of  this  tank  an  iron  pipe  which  passes  along  the 
tables.  The  tank  is  easily  filled  through  a  small  iron 
pipe  which  hooks  over  its  top  and  reaches  down  into 
the  sink,  where  it  may  be  connected  with  the  faucet 
by  a  piece  of  rubber  tubing. 

The  laboratory  should  also  contain  a  water  suction- 
pump,  a  mercury  air-pump,  a  barometer,  and  accurate 
thermometers.  An  electric  current  is  necessary,  and 
this  may  be  supplied  either  by  a  battery  or  storage 
cells,  or  the  direct  current  from  a  dynamo  may  be 
utilised.  A  small  induction  coil  is  needed  for  analy- 
ses of  gas  mixtures  by  explosion.  It  is  desirable  to 
have  narrow  shelves  fastened  to  the  wall  upon  which 
to  place  the  Hempel  pipettes. 


CHAPTER  VI 

PURIFICATION  OF  MERCURY 

DISTILLATION  IN  VACUUM 

ONE  of  the  best  methods  for  the  purification  of 
mercury  is  that  of  distillation  as  suggested  by  Wein- 
hold.1  Unfortunately  this  does  not  yield  a  perfectly 
pure  metal.  The  author  has  often  found  that  other 
metals  also  distil  over  in  vacuum. 

A  convenient  apparatus  for  the  distillation  is  that 
shown  in  Fig.  54.  This  corresponds  in  the  main  to 
Weinhold's  device,  but  has  some  modifications.  A  is 
a  bulb-tube,  ground  obliquely  at  the  end,  and  extend- 
ing to  the  bottom  of  the  wide  tube  D.  Through  a 
stopper  in  the  lower  end  of  D  is  inserted  from  below 
a  thin  glass  tube  about  1  m.  6  cm.  long,  which  reaches 
nearly  to  the  bottom  of  the  bulb  A.  The  tube  C  is 
bent  as  shown  in  the  figure,  and  has  at  a  a  side  tube 
with  glass  stopcock.  D  is  connected  by  a  branch 
tube  b  and  a  piece  of  rubber  tubing  with  the  level- 
vessel  J. 

To  start  the  apparatus  working,  the  end  of  the 
tube  C  is  closed  at  c  by  a  piece  of  rubber  tube  and  a 
pinchcock,  mercury  is  poured  into  <7,  and  the  appara- 
tus is  connected  at  a  with  a  mercury  air-pump. 

1  Carl's  Hep.  f.  Exp.-Physik,  15, 1.  Also  Fresenius  Zeitschrift 
f.  analyt.  Chemie,  18,  252. 

99 


100 


GAS  ANALYSIS 


PART  I 


As      the      air     is 
removed     from    the 
apparatus,  the    mer- 
cury passes   from  J 
toward  D  and  rises 
in  the  space  between 
the  tubes  A  and  O. 
When    the    mercury 
air-pump  yields  only 
quite   small   bubbles 
of  air,  the  exhaust- 
ing is  discontinued. 
The    level-vessel    J 
is  now  brought  into 
such  a  position  that 
the    mercury,  under 
the  prevailing  press- 
ure   of    the    atmos- 
phere,  fills   about   | 
of  the  bulb  A.     To 
facilitate  this  adjust- 
ment  the    board   E, 
which  hangs  upon  a 
nail     fastened     into 
the  wall,  has  a  num- 
ber   of    holes    bored 
through  it.      By  in- 
serting      the       nail 
through  one   or    an- 
other of  these  holes, 
the    position  of    the 
board  may  easily  be 
changed.    If  now  the 


FIG.  54. 


CHAP,  vi  PURIFICATION     jF  /M&RCjjJtt' , ;  \  -/  \     •>  >  :M 

bulb  is  heated  by  a  ring  burner,  the  mercury  soon 
begins  to  boil,  the  vapours  given  off  in  the  vacuum 
enter  the  tube  (7,  condense  there,  and  after  a  while 
the  length  of  the  column  of  mercury  which  has  col- 
lected in  the  tube  becomes  greater  than  the  height 
of  the  barometer.  A  bottle  for  receiving  the  puri- 
fied mercury  is  then  placed  under  (7,  and  the  rub- 
ber tube  and  pinchcock  closing  c  are  removed.  It  is 
advisable  to  stop  the  distillation,  and  after  the  appa- 
ratus has  cooled  somewhat,  to  exhaust  the  apparatus 
as  completely  as  possible  with  the  mercury  air-pump. 
In  this  second  exhaustion  a  considerable  quantity  of 
air  which  has  been  detached  from  the  walls  by  the 
heat  is  always  obtained.  The  apparatus  must  not  be 
exhausted  during  the  heating,  because  the  mercury 
may  break  the  whole  apparatus  by  violently  boiling 
when  the  pressure  is  decreased. 

The  ring  burner  B  is  made  from  a  bent  iron  tube 
pierced  with  little  holes,  a  circle  of  small,  slightly 
luminous  flames  being  thus  obtained.  A  small  screen 
of  asbestos  is  hung  above  the  bulb  to  check  the 
upward  radiation  of  heat. 

With  careful  use  the  apparatus  thus  arranged  may 
be  employed  for  years,  provided  that  the  mercury 
introduced  is  always  perfectly  dry.  To  effect  this 
the  impure  mercury  is  heated  in  an  iron  dish  to  120°- 
130°  C.  The  temperature  may  be  easily  ascertained 
by  using  a  thermometer  as  a  stirring  rod.  The  mer- 
cury thus  dried  is  poured  when  cool  into  the  flask 
jF,  and  this  is  closed  with  the  thumb  and  inverted 
in  the  level-vessel  J.  During  this  manipulation  the 
connecting  rubber  tube  d  is  closed  with  the  pinch- 
cock  H, 


GAS  ANALYSIS 


To   distil,  the   pinchcock  H  is   opened,  and  the 
apparatus  may  be  left  to  itself  for  twelve  hours,  the 
height  of  the  mercury  in  A  be- 
ing first  adjusted  by  bringing  the 
board  E  into  the  proper  position. 

PURIFICATION  OF  MERCURY  BY 
NITRIC  ACID 

Very  pure  mercury  is  obtained 
by  letting  it  fall  in  small  drops 
through  a  column  of  nitric  acid 
about  1  m.  high.  The  arrange- 
ment for  this  purpose  is  shown  in 
Fig.  55. 

A  is  a  glass  tube  from    2   to 
3    cm.    wide,    and    fitted   at   the 
lower  end  with  a  cork  and  the 
bent   glass    tube   D.      B  is   the 
supply   bottle   for    impure    mer- 
cury, and  C  the  receiver 
for  the  purified  mercury. 
Some  pure  mercury  is  first 
poured  into  the  tube  D, 
and  A  is  then  filled  with 
dilute  nitric  acid,  the  acid 
being  kept  in  the  tube  by 
the  pressure  of  the  mer- 
cury in  D.     Upon  allow- 
ing the  mercury  to  drop 
from-S,  the  purified  metal 
passes  slowly  over  into  (7, 


Fio.  55. 


CHAP,  vi  PURIFICATION   OF  MERCURY  103 

PURIFICATION  OF  MERCURY  BY  AIR 

According  to  Crafts,  mercury  is  completely  puri- 
fied by  leading  air  through  the  metal.  Leading  air 
through  for  forty-eight  hours  suffices  for  20  kg.  of 
mercury.  Zinc,  copper,  and  lead  are  completely 
changed  to  oxides.  The  mercury  thus  purified  does 
not  further  change  upon  exposure  to  the  air. 

Berzelius  had  already  noticed1  that  foreign  sub- 
stances may  be  removed  from  mercury  by  shaking  it 
with  air.  Maumene  has  used  the  method  for  the 
preparation  of  mercury  for  barometers.  He  put 
1  kg.  of  mercury  into  a  liter  bottle  and  fastened  the 
bottle  to  the  wheel  of  a  wagon.  After  driving  for 
a  few  minutes,  a  dust  of  the  foreign  metals,  mixed 
with  mercury,  was  formed. 

PURIFICATION   OF   MERCURY   BY   CONCENTRATED 
SULPHURIC  ACID  AND  MERCUROUS  SULPHATE 

This  is  one  of  the  most  convenient  of  all  the 
methods  that  have  been  suggested  for  the  purifica- 
tion of  mercury,  and  it  furnishes  at  once  a  pure  and 
dry  metal. 

The  process  of  purification  may  conveniently  be 
carried  out  in  a  heavy  separatory  funnel  of  from  2 
to  4  liters  capacity,  the  funnel  being  supported  in  a 
wooden  stand  at  such  a  height  that  an  ordinary 
bottle  or  beaker  may  easily  be  brought  under  its 
lower  end.  The  funnel  is  first  partially  filled  with 
mercury  (impure  mercury  may  be  used  here,  if  110 
purified  mercury  is  at  hand),  and  then  about  500  cc. 

1  Chemiker-Zeitung,  1888,  pp.  741,  808.    Ann.  de  Chim.  87,  144. 


104 


GAS  ANALYSIS 


PART  1 


of  concentrated  sulphuric  acid  is  poured  upon  the 
mercury  and  from  25  to  50  g.  of  mercurous  sulphate 

is  added.  In  the 
top  of  the  separa- 
tory  funnel  is  placed 
an  ordinary  funnel, 
the  stem  of  which  is 
drawn  out  to  small 
diameter  and  turned 
upward.  The  mer- 
cury to  be  purified 
is  poured  into  this 
latter  funnel  and 
flows  slowly  and  in 
the  form  of  a  fine 
spray  out  of  the  end 
of  the  stem.  It  is 
freed  from  foreign 
metals  by  the  ac- 
tion of  the  sulphuric 
acid  and  mercurous 
sulphate,  and  is 
thoroughly  dried  by 
passing  through  the 
concentrated  acid, 
so  that  pure  and 
dry  mercury  may  at 
any  time  be  drawn 
off  from  the  sepa- 
rator y  funnel.  In 

FIG.  56.  ,/ 

starting  the  process, 

impure-  mercury  which  may  first  have  been  put  into  the 
funnel  should,  of  course,  be  drawn  off  and  run  through 


CHAP,  vi  PURIFICATION   OF   MERCURY  105 

the  purifier  a  second  time.  The  mercury  in  the 
separatory  funnel  should  never  be  drawn  down  until 
it  is  near  the  stopcock,  for  there  might  then  be  dan- 
ger of  drawing  off  some  sulphuric  acid  with  it. 

A  somewhat  more  elaborate  apparatus  for  carry- 
ing out  this  purification  is  shown  in  Fig.  56.  It  con- 
sists of  two  bells  A  and  j5,  which  are  closed  at  the 
bottom  with  rubber  stoppers  provided  with  glass 
stopcocks.  The  upper  bell  B  is  filled  with  water,  and 
the  lower  contains  concentrated  sulphuric  acid  and 
mercurous  sulphate.  The  rubber  stopcocks  in  both  of 
the  bells  should,  of  course,  always  be  covered  by  some 
mercury.  The  impure  mercury  is  introduced  into  B, 
and  is  then  allowed  to  run  slowly  from  B  into  A.. 

REMARKS  UPON  THE  MAKING  OF  APPARATUS 

In  making  apparatus,  it  is  a  decided  mistake  to 
use  tubes  which  are  too  thick-walled,  for  such  tubes 
break  of  themselves,  without  other  cause,  upon  being 
exposed  to  slight  changes  of  temperature.  One  should 
further  avoid  fastening  the  apparatus  at  too  many 
places  to  the  wooden  or  iron  standards.  As  a  rule, 
the  glass  should  be  fastened  at  only  a  very  few  points, 
and  even  then  in  such  a  manner  that  a  free  expansion 
in  certain  directions  is  possible.  The  attachment  is 
best  made  by  fastening  a  metal  band  over  the  glass, 
but  not  touching  it,  and  filling  the  space  between  the 
board  and  the  glass  with  plaster  of  Paris.  If  it  is 
necessary  to  fuse  platinum  wires  in  the  glass,  very 
fine  wire  should  be  used.  It  is  easy  to  fuse  this 
into  the  glass  absolutely  gas-tight  without  the  use  of 
enamel,  while  thicker  wire  cannot  always  be  put  in 
perfectly  tight  even  by  an  expert  glass-blower. 


CHAPTER   VII 

ANALYSIS  WITH  THE   USE  OF  ORDINARY  ABSORP- 
TION APPARATUS 

GASES  which  are  very  easily  soluble  in  water,  e.g. 
ammonia,  chlorine,  sulphur  dioxide,  etc.,  are  best 
determined  by  leading  them  through  a  suitable  ab- 
sorption apparatus  and  ascertaining  their  amounts 
by  weighing  or  titration.  In  doing  this  it  is  neces- 
sary that  the  volume  of  the  gases  not  absorbed  be 
measured  by  an  appropriate  apparatus  placed  either 
before  or  behind  the  absorption  apparatus. 

This  method  of  analysis  is  especially  well  adapted 
to  the  determination  of  very  small  quantities  of  a  gas. 

In  analysing  a  gas  mixture  by  directly  determining 
the  volumes  of  the  constituents,  all  the  measurements 
must  be  made  with  the  same  sharpness  ;  but  when  the 
work  is  done  in  the  manner  above  mentioned,  a  much 
less  accurate  measurement  of  the  total  volume  suffices, 
correct  results  being  obtained  if  only  the  determina- 
tion of  the  gas  in  question  is  accurately  made. 

For  example,  in  determining  the  carbon  dioxide  in 
the  air  by  measuring  its  volume,  if  100  ccm.  of  air 
be  taken,  the  measurements  must  be  exact  to  the 
hundredths  of  a  cubic  centimeter,  even  if  one  wishes 
only  to  approximate  the  accuracy  demanded  in  analy- 
ses of  the  atmosphere.  But  by  using  a  standardised 
solution  with  which  the  gas  is  brought  into  contact, 
a  much  greater  accuracy  may  easily  be  obtained  even 

106 


CHAP,  vii  ABSORPTION  APPARATUS  107 

with  relatively  rough  measurement  of  the  initial 
volume. 

A  simple  calculation  will  best  make  this  clear. 

Let  us  suppose  that  10  liters  of  air  is  taken  for  the 
analysis,  and  that,  by  titration,  4  ccm.  of  carbon 
dioxide  is  found  to  be  contained  therein,  i.e.  0.04 
per  cent.  Suppose  further  that  a  mistake  of  10  ccm., 
which  would  be  an  enormous  experimental  error,  has 


FIG.  57. 

been  made  in  the  measurement  of  the  air.  The 
amount  of  carbon  dioxide  calculated  for  an  initial 
volume  of  10010  ccm.,  would  be  0.03996  per  cent,  or 
for  9990  ccm.  0.04004  per  cent. 

Let  us  suppose  further  that  in  using  burettes  which 
are  graduated  in  fifths,  the  error  in  reading  is  0.1  per 
cent ;  the  above  error  would  then  be  2J  times  as 
great  as  the  amount  of  CO2  present. 


108 


GAS  ANALYSIS 


PART  1 


From  this  it  follows  that  very  small  quantities  of  a 
gas,  mixed  with  large  volumes  of  other  gases,  should 
be  determined  if  possible  by  absorption  and  subse- 
quent weighing  or  titration. 

A  very  suitable  apparatus  for  the  absorption  of 
gases  is  the  absorption  tube  proposed  by  Pettenkofer 
(Fig.  57),  of  which  a  more  convenient  form  has  been 
devised  by  Winkler  (Fig.  58).  If  gases  only  are  to 
be  absorbed,  the  Pettenkofer  tube  is  admirably  suited 
to  the  purpose.  If,  however,  the  gases  contain  sub- 
stances in  the  form  of  dust,  a  complete  absorption  is 
not  obtained  ;  in  such  cases  the  gas  bubbles  must  be 
broken  up,  this  being  done  by  means  of  a  long  per- 
pendicular glass  tube  filled  with  glass  beads.  A 
convenient  device  for  this  purpose  is  a  combination 

of  such  a  tube  with  a  Peli- 
got  tube  (Fig.  59). 

If  the  vessel  may  be 
shaken  during  the  absorp- 
tion, a  simple  Woulf  bottle 
answers  every  purpose. 

To  absorb  large  amounts 
of  gases  the  apparatus  de- 
vised by  Winkler  may  ad- 
vantageously be  used.  He 
obtains  a  large  surface  of 
contact  by  employing  light 
and  porous  pumice-stone, 
and  the  absorption  appara- 
tus he  uses  has  the  form 
shown  in  Fig.  60.  The 

cylinder  a  has  two  openings  at  the  top,  and  it  ends  at 
the  bottom  in  a  tube  which  is  ground  into  the  neck 


FIG.  58. 


CHAP.  VII 


ABSORPTION  APPARATUS 


109 


of  the  Woulf  bottle  b.  The  bottle  contains  the  ab- 
sorbing liquid,  and  a  is  filled  with  pieces  of  pumice- 
stone.  Upon  blowing  into  d  the  liquid  is  made  to 
rise,  the  pumice-stone  becoming  thereby  thoroughly 
moistened.  Upon  reopening  d  the  excess  of  liquid 


FIG.  59. 


FIG. 


flows  back  into  6,  and  the  apparatus  is  ready  for  the 
absorption.  The  gas  enters  through  the  tube  <?, 
which  extends  as  far  as  the  narrow  part  of  a,  and 
then  rising  through  the  moistened  pumice-stone  it 
passes  out  at  e. 


110 


GAS  ANALYSIS 


PART 


Reiset l  has  constructed  a  very  effective  absorption 
apparatus  for  the  determination  of  carbon  dioxide  in 
the  atmosphere,  this  device  rendering  it  possible  to 
work  with  very  large  volumes  of  air  (600  liters). 
The  construction  is  shown  in  Fig.  61.  Jis  a  U-tube 
filled  with  pieces  of  pumice-stone  moistened  with  con- 
centrated sulphuric  acid.  At  the  lower  end  of  the 


FIG 


tube  is  a  bulb  in  which  collects  the  dilute  sulphuric 
acid  that  would  otherwise  retard  the  passage  of  the 
air.  This  tube  /acts  as  a  drying  tube  ;  it  holds  back 
the  total  moisture  of  the  air  used  in  the  experiment, 
and  its  increase  of  weight  gives  the  percentage  of 
moisture  in  the  air.  The  dried  gas  now  passes  into 
the  absorption  apparatus  proper  through  the  tube  t 


1  Comptes  rendus, 
4,  485. 


I,  1007  ;  and  90,  144.      Chemiker-Zeitung, 


CHAP,  vii  ABSORPTION  APPARATUS  111 

which  is  fastened  into  the  neck  of  the  bottle  F.  This 
part  of  the  apparatus  is  based  upon  the  principle  which 
Schlosing  made  use  of  to  absorb  the  ammonia  in  the 
atmosphere,  and  to  facilitate  its  quantitative  determi- 
nation. Three  slightly  conical  little  boxes,  <7,  <7',  and  0' 
(Fig.  61),  made  from  thin  platinum  foil,  are  pushed 
into  the  glass  cylinder  T^  the  friction  with  the  sides  of 
the  tube  holding  them  in  place.  Each  little  box  has 
a  diameter  of  4  cm.,  and  is  pierced  with  120  holes 
of  about  0.5  mm.  diameter,  ^is  0.5  m.  long.  It  is 
joined  to  F  by  means  of  a  thick,  tightly  fitting  rubber 
ring  J.  Before  beginning  the  analysis  300  ccm.  of  a 
clear  standardised  solution  of  baryta  water  is  put 
in  the  tube.  The  tube  is  then  connected  air-tight 
with  the  U-tube  ZZ,  which  is  filled  in  exactly  the 
same  manner  as  Z,  and  the  aspirating  is  begun. 

At  the  end  of  the  experiment,  that  is,  after  600 
liters  of  air  had  passed  through,  Reiset  found  the 
baryta  water  in  the  bottle  and  in  the  lowest  part  B 
of  the  cylinder  completely  charged  with  carbonate, 
that  in  B1  only  milky,  while  the  solution  in  B"  was 
clear  and  transparent  —  a  proof  that  the  carbon 
dioxide  was  completely  absorbed. 

The  baryta  water  is  now  brought  into  a  bottle 
supplied  with  a  tightly  fitting  stopper,  and  the  cylin- 
der and  bottle  are  carefully  rinsed  with  known  quan- 
tities of  water. 

The  U-tube  II  is  weighed,  and  the  amount  of 
water  carried  over  from  the  baryta  water  is  thus 
determined.  The  barium  carbonate  is  allowed  to 
settle,  and  as  the  total  amount  of  liquid  is  now  known, 
a  titration  of  a  measured  portion  of  the  clear  solution 
gives  the  amount  of  unchanged  barium  hydroxide, 


112 


GAS   ANALYSIS 


PART  I 


and,  by  a  simple  calculation,  the  per  cent  of  carbon  di- 
oxide in  the  atmosphere.  (The  measured  volume  of  air 
is  of  course  always  reduced  to  0°  and  760  mm.  pressure). 
•  For  measuring  gases  a  gas-meter  or  simple  aspi- 
rator is  employed.  The  measurement  can  be  made 
very  simply  by  calculating  the  gas  volume  from  the 
amount  of  water  which  has  flowed  from  the  aspirator, 
with  corrections  for  temperature  and  barometric 
pressure. 


Fio.  62. 

Figure  62  shows  such  an  arrangement.  A  is  a 
Pettenkofer  tube,  B  is  a  bottle  which  can  be  emptied  by 
the  glass  siphon  a,  (7  is  a  graduated  bottle.  To  make 
a  determination,  bring  an  accurately  measured  amount 
of  reagent  into  the  absorption  tube,  open  the  siphon, 
and  measure  the  quantity  of  water  which  passes  over, 
beginning  the  measurement  at  that  moment  when  the 
first  bubble  passes  from  b  into  the  absorbing  liquid. 


PAET   II 

SPECIAL  METHODS 


CHAPTER   I 

GENERAL  REMARKS  UPON  ABSORPTION  ANALYSES 
WITH  THE  APPARATUS  FOR  TECHNICAL  GAS 
ANALYSIS 

THE  accuracy  which  may  be  attained  by  simple 
absorptions  carried  out  in  the  apparatus  previously 
described  is  so  great,  even  when  the  analyses  are 
made  over  aqueous  solutions,  that  it  is  but  slightly 
inferior  to  the  exact  analyses  made  over  mercury, 
and  in  all  cases  completely  satisfies  the  demands  made 
upon  the  technical  chemist. 

For  the  sake  of  comparison,  two  partial  analyses 
by  this  method  and  an  exact  analysis  over  mercury 
(see  Part  I.  Chap.  IV.  .#)  are  here  given;  the  gas 
used  in  each  case  is  illuminating  gas,  taken  September 
23,  1877. 

I.  Technical         II.  Technical  Exact  Analysis  over 

Analysis    '  Analysis  Mercury 

1.6  per  cent        1.5  per  cent        1.5  per  cent  carbon  dioxide 

3.1        «  2.9        "  3.0       «         heavy  hydrocarbons 

1.4       "  1.6        "  '  1.4       "        oxygen. 

Errors  so  large  that  they  may  entirely  destroy  the 
value  of  the  analysis  result  when  the  apparatus  and 
the  reagents  do  not  have  the  temperature  of  the 
laboratory,  or  when  the  temperature  changes  during 
the  brief  time  necessary  for  the  analysis.  Since,  for 

115 


116  GAS   ANALYSIS  PART  n 

example,  a  rise  of  temperature  of  only  one  degree 
would  cause  an  error  of  0.3  per  cent  in  a  total 
volume  of  100  ccm.,  it  follows  that  working  near 
a  stove,  boiler,  fire,  etc.,  is  wholly  inadmissible,  and 
that  the  apparatus  and  confining  liquids  must  be 
kept  at  the  place  where  the  analysis  is  made. 

It  is  of  no  less  importance  for  the  obtaining  of 
accurate  results  that  the  confining  liquids  be  allowed 
to  flow  down  from  the  walls  of  the  burette  in  exactly 
the  same  manner  after  each  absorption.  Otherwise  an 
error  may  be  caused  by  the  adhering  of  more  or  less 
liquid  to  the  glass  walls.  One  can  easily  convince 
himself  by  experiment  that,  with  gases  confined  over 
water,  readings  which  are  made  one  minute  after  the 
gas  has  been  shaken  with  water  in  the  burette  differ 
by  several  tenths  of  a  cubic  centimeter  from  readings 
made  five  minutes  later.  With  all  other  liquids,  such 
as  caustic  alkalies,  cuprous  chloride,  concentrated  sul- 
phuric acid,  etc.,  the  running-down  takes  place  much 
more  slowly,  so  that  an  error  of  one  cubic  centimeter 
or  more  may  result.  The  condition  of  the  glass  plays 
an  important  part  here,  as  in  all  adhesion  phenomena. 
An  invisible  layer  of  salt  or  fat  acts,  of  course,  quite 
differently  from  the  clear  glass  surface. 

The  author  has  found  by  repeated  experiment 
that  distilled  water  will  run  down  completely  in  five 
minutes,  while  a  five  per  cent .  solution  of  sodium 
hydroxide  requires  ten  minutes,  and  concentrated 
sulphuric  acid  from  fifteen  to  twenty.  For  this 
reason,  rapid  and  at  the  same  time  accurate  work 
is  quite  impossible  in  all  those  forms  of  apparatus 
in  which  the  gas  is  not  always  measured  over  the 
same  liquid. 


CHAP,  i     ACCURACY   OF  TECHNICAL  ANALYSIS  117 

In  the  method  previously  given,  the  gases  pass 
from  the  pipettes  into  the  measuring  burette  in 
nearly  equal  periods  of  time,  or  in  time  proportional 
to  the  volume  of  the  gases,  since  the  connecting 
capillary  acts  as  a  regulator,  and  also  since  the 
adhesion  of  the  water  in  the  burette  does  not  vary 
during  the  analysis.  For  these  reasons  the  reading 
may  be  taken  either  shortly  after  the  gas  has  been 
drawn  back  into  the  burette,  or  after  the  water  has 
run  down,  and  good  results  may  be  obtained  in  both 
cases.  The  most  accurate  results  are  naturally  ob- 
tained from  readings  taken  after  the  water  has  run 
down  completely. 

Confirmatory  Analyses 

Partial  analysis  of  a  sample  of  illuminating  gas 
taken  September  13,  1877. 

I.  100  ccm.  of  gas  were  taken. 

The  readings  were  made  five  minutes  after  passing 
the  gas  back  into  the  measuring  burette ;  that  is, 
after  complete  running  down  of  the  water. 

Results  — 

2.4  per  cent  carbon  dioxide 

3.4       "         heavy  hydrocarbons 

0.8        "         oxygen 

8.1        "         carbon  monoxide. 

II.  The   readings   were   made   one   minute   after 
passing  the  gas  back,  the  running  down  of  the  water 
not  being  waited  for. 

Beginning  of  the  analysis,  10.36  A.M. 
End  "  "         11.14     " 


118  GAS  ANALYSIS  .PART  n 

Results  — 

2.0  per  cent  carbon  dioxide 

3.3       "        heavy  hydrocarbons 
0.7       "        oxygen 

8.1  "        carbon  monoxide. 


CHAPTER   II 

CONCERNING   THE    SOLUBILITY  OF   GASES    IN   THE 
ABSORBENTS 

THERE  is  no  doubt  that  working  with  unsaturated 
absorbing  liquids  leads  to  the  most  erroneous  results, 
and  that  on  account  of  the  variation  of  temperature 
and  pressure  the  highest  scientific  accuracy  can  be 
attained  only  by  working  over  mercury  and  with 
solid  absorbents.  In  by  far  the  greater  number  of 
cases,  however,  the  use  of  aqueous  solutions  is  possi- 
ble if  they  are  allowed  to  become  saturated  in  the 
manner  mentioned  on  p.  53. 

It  would  be  a  decided  mistake  if,  for  example,  in 
an  analysis  of  a  mixture  of  carbon  dioxide,  nitrous 
oxide,  and  nitrogen,  the  absorbing  liquid  were  satu- 
rated with  nitrous  oxide  by  leading  the  pure  gas 
through  the  absorbent,  and  thus  bringing  it  into  con- 
tact with  the  liquid  at  the  pressure  of  an  atmosphere. 
The  error,  however,  is  very  small  if  the  absorbent  is 
saturated  in  such  a  manner  that  the  amounts  of  dis- 
solved gases  correspond  exactly  to  the  partial  pressure 
which  the  various  constituents  will  exert  in  the  analy- 
sis to  be  made.  Although  this  may  not  be  possible 
in  a  theoretical  sense,  yet  in  most  cases  it  may  be  ac- 
complished to  a  quite  sufficient  degree  by  making, 
with  the  same  absorbent,  two  or  three  analyses  of  the 
same  gas  mixture,  one  directly  after  another.  It  is 

119 


120  GAS  ANALYSIS  PART  n 

precisely  this  consideration  which  gives  the  great 
exactness  to  the  work  with  the  pipettes  devised  by 
the  author,  an  exactness  that  cannot  be  attained 
with  the  simple  gas  burettes.  In  the  examination  of 
industrial  gases,  where  repeated  analyses  of  nearly 
identical  gas  mixtures  are  made,  the  pipettes  remain 
of  themselves  sufficiently  saturated,  so  that  a  double 
analysis  is  generally  unnecessary.  Parallel  analyses, 
made  by  the  author,  over  water  on  the  one  hand  and 
over  mercury  on  the  other,  serve  to  confirm  the  state- 
ment given  above. 

The  determination  of  carbon  monoxide  in  a  gas 
gave  — 

With  unsaturated  reagent  — 

8.6  and  8.5  per  cent. 
With  saturated  reagent  — 

8.1  and  8.0  per  cent. 

Two  partial  analyses  of  a  sample  of  illuminating 
gas  taken  April  24,  1879,  gave  — 
With  unsaturated  confining  water  — 

3.5  per  cent  carbon  dioxide 

4.6  "        heavy  hydrocarbons 

11.2  *'        carbon  monoxide. 

With  saturated  confining  water  — 

3.3  per  cent  carbon  dioxide 

4.6       "        heavy  hydrocarbons 

10.3  "        carbon  monoxide. 

Washing  out  the  reagents  from  the  burette  with 
water,  as  several  writers  have  proposed,  is  thus  quite 
impracticable,  as  one  may  easily  convince  himself  by 


CHAP,  ii     SOLUBILITY   OF   GASES  IN   ABSORBENTS      121 

comparing  results  so  obtained  with  those  given  by  an 
exact  analysis. 

If  an  analysis  need  be  accurate  only  to  within  0.5 
per  cent,  it  is  unnecessary  to  first  saturate  the  con- 
fining water  with  the  gas  under  examination. 

Errors  much  larger  than  those  mentioned  above  — 
so  large,  in  fact,  as  to  give  completely  misleading  re- 
sults—  arise  from  faulty  arrangement  of  the  appa- 
ratus in  taking  the  sample. 


CHAPTER   III 
CONCERNING  THE  COMBUSTION  OF  GASES 

SINCE  absorbents  for  all  gases  are  not  as  yet 
known,  the  combustion  of  certain  inflammable  gases 
is  an  operation  of  great  importance. 

The  heating  of  the  gases  to  the  temperature  of  com- 
bustion from  within  the  mixture  is  accomplished  either 
by  an  electric  spark,  the  combustion  then  taking  place 
in  an  instant  as  an  explosion,  or  by  means  of  an  elec- 
trically heated  platinum  spiral  which  is  brought  to 
glowing  in  the  gas  mixture. 

The  gas  can  also  be  heated  from  without  by  lead- 
ing it  through  a  tube  of  glass  or  platinum  which  is 
heated  to  glowing  by  a  flame. 

By  means  of  the  combustion,  the  nature  and  volume 
of  the  elementary  constituents  of  a  single  combustible 
gas  of  unknown  composition  and  its  molecular  struc- 
ture may  be  determined. 

Bunsen  has  stated  the  theoretical  data  in  his  G-aso- 
metrische  Methoden,  2d  ed.,  1877,  pp.  48-51. 

If,  in  this  question,  we  start  with  the  most  com- 
plicated case,  viz.,  that  in  a  volume  of  a  gas  there  are 
x  vol.  of  gaseous  carbon,  y  vol.  hydrogen,  z  vol.  oxy- 
gen, and  n  vol.  nitrogen,  then  four  equations  are 
necessary  for  determining  x,  y,  z,  and  n.  To  obtain 
these  four  equations  it  suffices  to  burn  a  volume  V  of 

122 


CHAP,  in  THE   COMBUSTION  OF  GASES  123 

the  gas  in  question,  and  then  to  determine  (1)  the 
contraction  C  resulting  from  the  combustion;  (2) 
the  aqueous  vapour  Y  which  has  been  formed  ;  (3) 
the  resulting  carbon  dioxide  X;  and  (4)  the  sepa- 
rated nitrogen  S. 

The  gaseous  carbon  x  contained  in  a  unit  volume 
of  the  gas  gives  2x  carbon  dioxide,  and  V  volumes 
give  2zV.  Hence 


or 


The  hydrogen  y  contained  in  one  volume  of  the 
gas  gives  y  volumes  of  aqueous  vapour,  V  volumes 
give  Vy.  Hence 

Y  =  yV,     or     3,=|. 

Since,  further,  in  a  unit  volume  of  the  gas  there 
are  n  volumes  of  nitrogen,  and  in  V  volumes  Vn 
nitrogen,  it  follows  that 

S  =  Vrc,     or     n  =  —  . 

Finally  the  volume  of  gas  before  the  combustion  is 
made  up  of  the  gas  volume  V  and  the  oxygen  volume 
O  which  has  been  added.  The  gas  volume  remain- 
ing after  the  combustion  is  equal  to  the  oxygen  vol- 
ume O  added,  minus  the  oxygen  volume  2  x  necessary 
to  the  formation  of  the  carbon  dioxide,  minus  the 
oxygen  volume  \y  necessary  for  the  formation  of  the 
water,  plus  the  volume  of  the  carbon  dioxide  formed 
2  z,  plus  the  oxygen  volume  z  contained  in  the  original 
gas,  plus  the  nitrogen  volume  n  separated  from  the 


124  GAS   ANALYSIS  PART  n 

gases    by    the    combustion.      Substituting   now   the 
values  found  for  #,  #,  and  n,  we  have  — 

As  volume  before  the  combustion,  V  +  O  ; 

Y  S 

As  volume  after  the  combustion,  O  ---  \-  z  +  —  . 

Subtracting  the  lower  expression  from  the  upper, 
there  results,  for  the  gas  volume  which  has  disap- 
peared — 


To  determine  V,  X,  Y,  S,  and  C  by  experiment,  V 
volumes  of  the  gas  under  examination  are  brought 
into  the  explosion  eudiometer,  an  amount  of  oxygen 
O  necessary  for  the  combustion  is  added,  and  the 
mixture  then  ignited.  The  reduced  gas  volume  dis- 
appearing in  the  explosion  is  C. 

The  eudiometer  is  now  heated  to  100°  C.  in  a  suita- 
ble apparatus.  The  difference  between  the  reduced 
volumes  before  and  after  the  heating  is  Y. 

The  volume  of  carbon  dioxide  X  is  next  determined 
by  means  of  a  potash  ball.  The  residue  now  in  the 
eudiometer  consists  of  nitrogen  mixed  with  an  un- 
known amount  of  oxygen.  This  latter  is  determined 
by  combustion  with  hydrogen,  and  is  subtracted,  and 
the  volume  of  nitrogen  is  thus  found. 

If  chemical  tests  show  that  the  gas  contains  no 
oxygen,  i.e.  that  2=0,  then 

°  =  v-c  +  X_s. 


CHAP,  in  THE   COMBUSTION  OF   GASES  125 

substituting  the  value  V#  for  Y,  there  results  — 

0=V+|-C-|,    or    y  = 

With  the  aid  of  this  equation  the  hydrogen  con- 
tained in  a  unit  volume  of  a  gas  free  from  oxygen 
may  be  calculated  from  the  contraction,  the  direct 
determination  of  the  volume  of  aqueous  vapour  Y 
being  thus  rendered  unnecessary. 

The  method  holds  good  for  nitrogen,  oxygen, 
hydrogen,  and  all  gases  of  the  following  composi- 
tion :  — 

n  vol.  C  +  n^  vol.  N  =  1  vol. 
n    "    GJ  +  W!    "    O  =  l    " 
n    "    C+T&     "    H  =  l    " 


n 

n  "  H  +  W!  "  N  =  l  " 

w  "  N+W!  "  O  =  l  " 

n  vol.  C  +  wx  vol.  H  +  n2  vol.  O  =  1  vol. 

n    "    C-f-^  "  H+^2  "  N=l  " 

n    "    H-f/ij  "  O  +  w2  "  N  =  l  " 

n    "    G      W  "  O      w  "  N  =  l  " 


It  is  seen  that  in  this  list  of  gases  there  are  some, 
namely  O  and  n  vol.  N  -f  n^  vol.  O  =  1  vol.,  which 
contain  no  constituent  combustible  with  oxygen. 
With  such  gases  hydrogen  must  be  added  for  the 
combustion  instead  of  oxygen.  If  V  is  the  initial 
volume,  C  the  gas  volume  disappearing  in  the  com- 


126  GAS  ANALYSIS  PART  11 

bustion,  and  H  the  hydrogen  added,  we  then  have 
as  — 

Vol.  before  the  combustion 


and  after  the  combustion  the  volume  will  be  — 

The  hydrogen  added,  minus  twice  the  volume  of 
the  oxygen  in  the  gas,  plus  the  remaining  nitro- 
gen, or 

(2)  U-2z  +  n. 

Subtracting  (2)  from  (1)  we  get 


It  is  thus  possible  on  the  one  hand  to  determine 
the  molecular  constitution  of  a  gas  by  combustion, 
while,  on  the  other  hand,  the  quantitative  propor- 
tions of  the  various  constituents  of  a  gas  mixture 
whose  qualitative  composition  is  already  known,  can, 
of  course,  be  ascertained  by  combustion. 

By  experiment  can  be  determined  — 

1.  The  total  contraction  caused  by  the  burning  of 
the  gases. 

2.  The  water  formed  in  the  combustion. 

3.  The  carbon  dioxide  formed  in  the  combustion. 

4.  The  oxygen  used  in  the  combustion. 

5.  The  nitrogen  remaining  after  the  combustion. 
Five  equations  may  be  made  from  these  experi- 

mental figures  thus  derived  and  from  the  known 
combustion  relations  of  the  gases  ;  hence,  by  means 
of  a  single  combustion  of  a  gas  mixture  containing 


CHAP,  in  THE  COMBUSTION  OF  GASES  127 

five  different  gases  which  are  qualitatively  known, 
the  amounts  of  these  five  gases  may  be  determined. 

Since  we  can  sharply  separate  most  gases  by  means 
of  absorbents,  the  combustion  is  generally  used  only 
for  the  separation  of  nitrogen  from  hydrogen,  marsh- 
gas,  and  the  higher  members  of  the  marsh-gas  series. 

Of  especial  significance  is  Bunsen's  discovery  that 
nitrogen  and  oxygen,  in  very  violent  explosions,  com- 
bine directly  to  form  nitric  oxide  or  nitrogen  tetroxide 
and  nitric  acid.  Bunsen  found  that  — 

100  vol.  of  air  with  13.45  oxyhydrogen  would  not 
burn. 

Vol.  of  Air 
remaining 

100  air  burned  with  26.26  oxyhydrogen  gas,  left     100.02 

100  «  "  34.66  «  «  100.15 

100  «  "  43.72  «  "  100.07 

100  «  "  51.12  «  "  99.98 

100  "  "  64.31  «  "  99.90 

100  "  "  78.76  "  «  99.43 

100  «  "  97.84  "  "  96.92 

100  "  "  226.04  "  «  88.56 

Bunsen  seeks  to  avoid  the  inaccuracies  which  exist 
in  many  of  the  older  gasometric  results  by  never 
using  in  his  experiments,  more  than  26  to  64  volumes 
of  combustible  gas  to  100  volumes  of  incombustible 


These  figures  give  us  undoubtedly  a  sharp  dividing 
line,  but  the  author  would  call  attention  to  the  fact 
that  they  do  not  hold  good  in  all  cases.  The  author 
has  ascertained  by  experiment  that  the  explosion 
phenomena,  when  marsh-gas  and  oxygen  or  carbon 
monoxide  and  oxygen  are  used,  are  quite  different, 
and  call  for  different  proportions  of  gas. 


128  GAS  ANALYSIS  PART  n 

The  gases  named  give  less  violent  explosions.  By 
following  Bunsen's  directions  it  is  possible  that  the 
gas  mixture  may  not  at  times  be  sufficiently  explo- 
sive, but  it  has  long  been  supposed  that  under  the 
conditions  which  he  laid  down,  the  burning  of  any 
nitrogen  present  would  always  be  avoided.  Accord- 
ing to  L.  Ilosvay,1  however,  the  union  of  nitrogen 
and  oxygen  takes  place  in  the  flame  of  the  Bunsen 
burner  even  when  carbon  dioxide  is  introduced  into 
the  flame  to  lower  its  temperature,  and  he  states  that 
oxides  of  nitrogen  are  also  formed  when  air  burns  in 
an  atmosphere  of  illuminating  gas.  A.  H.  White  2 
states  that  oxides  of  nitrogen  are  always  formed  in 
explosion  analyses  in  amount  increasing  with  the 
violence  of  the  explosion. 

By  practice  one  very  quickly  learns  to  judge  from 
the  appearance  of  the  flame  caused  by  the  explosion 
as  to  whether  the  explosion  has  been  strong  enough. 
For  complete  combustion  it  is  necessary  that  an 
active  explosion  take  place.  In  incomplete  com- 
bustion the  progress  of  the  flame  in  the  gas  mixture 
can  be  followed  by  the  eye. 

Every  combustible  gas  when  mixed  with  air  is 
inflammable  only  within  certain  limits.  The  follow- 
ing percentages  of  gases  when  present  in  a  mixture 
with  air  will  burn  :  — 

5  to  13  per  cent  CH4 

3  «  82        «        C2H2 

4  «  22        «        C2H4 

5  «  72        «        H 


1  Bull.  Soc.  Chim.,  1889,  p.  737. 

2  J.  Am.  Chem.  Soc.,  23,  476. 


CHAP,  in  THE  COMBUSTION  OF  GASES  129 

13  to  75  per  cent  CO 

9  "  55        "        water  gas 

5  "  28        "        illuminating  gas 

6  «  13.4     «        oil  gas 

A  "  15.5     "        mixed  gas  containing 
25  per  cent  CaH^  and 
75       "        oil  gas 
11.9  to  28.5     "        COS. 

If  larger  amounts  of  gas  are  available,  they  may  be 
burned  by  mixing  them  with  air  or  with  oxygen, 
leading  them  over  heated  copper  oxide,  and  weighing 
the  carbon  dioxide  and  water  formed.  R.  Fresenius 
suggests1  the  use  of  a  combustion  tube  about  30  cm. 
long  and  not  too  wide,  filled,  without  a  canal,  with 
coarse-grained  copper  oxide.  The  copper  oxide  is 
held  closely  together  by  means  of  stoppers  of  asbestos, 
about  7  cm.  long,  inserted  in  each  end  of  the  tube. 
The  asbestos  must  first  be  ignited  in  moist  and  then 
in  dry  air.  The  tube  is  wrapped  with  wire  gauze,  and 
is  heated  to  red  heat  in  a  small  combustion  furnace. 
The  gas  and  the  air  or  oxygen  necessary  for  the 
combustion  are  led  over  soda-lime  or  calcium  chlo- 
ride, and  it  is  best  to  bring  them  together  after  they 
have  entered  the  combustion  tube,  the  gases  entering 
the  tube  separately  through  the  two  openings  of  a 
rubber  stopper.  The  gas  must  previously  be  accu- 
rately measured.  The  water  formed  in  the  combus- 
tion is  absorbed  in  a  calcium  chloride  tube,  and  the 
carbon  dioxide  in  a  Liebig  potash  bulb. 

The  combustion  may  be  made  in  a  much  simpler 
manner  by  explosion  in  pipettes. 

1  Zeitschrift  fur  analytische  Chemie,  3,  339. 


130  GAS  ANALYSIS  PART  n 

THE   EXPLOSION   PIPETTE   FOR  TECHNICAL   GAS 
ANALYSIS  (Fio.  63) 

This  consists  of  the  thick-walled  explosion-bulb  a 
and  the  level-bulb  5,  which  are  joined  together  by 
a  wrapped  piece  of  rubber  tubing.  At  c  two  fine 
platinum  wires  are  fused  into  the  explosion  pipette, 
the  ends  of  the  wires  being  about  2  mm.  apart.  At 
c?  is  a  glass  stopcock,  and  the  pipette  terminates  in 


FIG.  63. 


the  capillary  e,  whose  end  is  closed  by  a  short  piece 
of  rubber  tubing  and  a  pinchcock.  In  general,  the 
pipettes  and  burettes  for  technical  gas  analysis  are 
filled  with  aqueous  solutions,  but  the  explosion  pipette 
is  filled  with  mercury.  By  using  mercury  as  con- 
fining liquid  during  the  explosion  it  is  possible 
afterward  to  determine  the  carbon  dioxide  formed  in 


CHAP.    Ill 


THE   COMBUSTION   OF   GASES 


131 


the  combustion.  If  the  explosion  is  made  over  water, 
a  subsequent  measuring  of  the  carbon  dioxide  formed 
is  inadmissible,  because  the  pressure  in  the  pipette 
is  so  high  during  the  explosion  that  considerable 
quantities  of  carbon  dioxide  are  absorbed  by  the 
water.  By  exploding  over  mercury  very  satis- 
factory results  are  obtained,  even  if  the  carbon 
dioxide  is  afterward 
measured  in  a  burette 
which  is  filled  with 
water. 

One  is  often  called 
upon  to  analyse  gas 
mixtures  which  do  not 
contain  sufficient  com- 
bustible ingredients  to 
make  them  explosive 
when  mixed  with  oxy- 
gen or  air;  in  such 
cases  combustibility  is 
produced  by  adding 
pure  hydrogen. 

The  hydrogen  is 
made  in  the  hydrogen 
pipette  (Fig.  64).  This 
is  a  simple  absorption 
pipette  which  has  two 
bulbs  in  the  place  of 

the  first  large  bulb.  Through  the  tube  g  a  glass  rod 
h  is  pushed  up  to  the  mouth  of  e.  This  rod  is  fas- 
tened tightly  into  g  by  means  of  a  piece  of  rubber 
tube  slipped  over  it,  and  it  serves  to  hold  pieces  of 
chemically  pure  zinc  in  the  bulb  e.  To  fill  the 


FlG 


132  GAS  ANALYSIS  PART  11 

pipette  it  is  inverted,  the  glass  rod  is  taken  out,  and 
the  pieces  of  zinc  are  dropped  into  e.  The  pipette 
is  then  closed  again,  placed  upright,  and  filled  with 
diluted  sulphuric  acid  (1.10)  by  means  of  a  funnel. 
The  pipette  is  closed  at  i  with  a  piece  of  rubber 
tubing  and  a  pinchcock. 

After  a  short  time  the  hydrogen  produced  will 
drive  back  the  acid,  so  that  the  evolution  ceases. 
Before  drawing  off  the  sample  of  hydrogen  from  the 
pipette  it  is  advisable  to  connect  with  the  capillary  i 
a  gas  burette,  and  to  draw  off  the  gas  in  the  pipette 
until  the  bulb  e  is  completely  filled  with  sulphuric 
acid.  A  new  supply  of  pure  hydrogen  is  now  gener- 
ated, and  this  gas  may  be  used  in  the  analysis.  If 
several  analyses  are  made  one  after  another,  this  fresh 
evolution  of  the  gas  is  unnecessary ;  but  if  the  appara- 
tus has  stood  for  any  length  of  time,  air  will  diffuse 
through  the  sulphuric  acid,  and  some  oxygen  and 
nitrogen  will  be  found  in  the  first  portion  of  hydro- 
gen that  is  drawn  off.  To  obtain  a  more  active 
evolution  of  hydrogen  than  that  which  takes  place 
when  pure  zinc  and  pure  acid  are  used,  a  few  pieces 
of  platinum  foil  may  be  put  in  with  the  zinc. 


THE  EXPLOSION  PIPETTE  FOR  THE  APPARATUS 
FOR  EXACT  ANALYSIS  (FiG.  65) 

In  the  exact  analysis  also  it  is  most  convenient  to 
make  the  explosions  in  a  pipette  especially  constructed 
for  the  purpose.  This  pipette  differs  from  the  ordi- 
nary pipettes  only  in  having  a  stopcock  at  a  and  two 
platinum  wires  fused  in  at  b. 


CHAP.    Ill 


THE   COMBUSTION   OF   GASES 


133 


To  burn  a  gas  mixture  in  this  apparatus,  the  gas 
is  brought  into  it  in  the  usual  manner,  the  stopcock 
is  closed,  and  a  fine  sewing  needle  is  placed  in  the 
mouth  of  the  capillary  c.  Upon  connecting  the  plati- 


FIG.  65. 


FIG.  66. 


num  wires  with  an  induction  apparatus,  the  mixture 
is  exploded  by  the  spark  which  passes  when  the 
circuit  is  closed. 

Hydrogen  is  made  in  the 


HYDROGEN  PIPETTE  (FiG.  66) 

the  construction  of  this  pipette  resembling  that  of 
the  hydrogen  pipette  shown  and  described  on  page 
131.  ' 

The  most  suitable  apparatus  for  the  evolution  of 
oxyhydrogen  gas  is  one  closely  resembling  the  Bun- 
sen  apparatus, 


134 


GAS   ANALYSIS 


PART    II 


THE   OXYHYDROGEN   GAS   GENERATOR 

The  author  has  found  that  in  the  evolution  of 
oxyhydrogen  gas  there  is  always  formed  some  ozone, 
which  upon  being  passed  through  mercury  unites 
with  the  metal.  For  this  reason  oxyhydrogen  gas, 

in  which  the  ozone  has  not 
been  previously  decom- 
posed, leaves  a  slight 
residue  of  hydrogen  when 
one  works  over  mercury. 
If  the  oxyhydrogen  gas  is 
collected  over  potassium 
iodide,  iodine  is  set  free 
even  after  the  evolution 
has  proceeded  for  some 
hours.  A  direct  experi- 
ment gave  0.7  ccm.  of 
free  hydrogen  in  a  liter 
of  the  gas.  The  ozone 
is  removed  either  by  put- 
ting the  apparatus,  during 
the  evolution,  into  water 
heated  to  90°,  or  by  ex- 
posing the  oxyhydrogen 
gas,  before  using  it,  to  the 
action  of  diffused  daylight 
for  12  hours,  whereby  the  ozone  disappears  of  itself. 
The  latter  way  is  the  more  convenient,  and  hence  in 
the  apparatus,  Fig.  67,  the  bulb  c  of  about  50  ccm. 
capacity  is  interposed  between  the  delivery  tube  b 
and  the  vessel  a.  When  the  apparatus  is  put  into 
use,  it  is  filled  by  a  rapid  evolution  of  oxyhydrogen 


FIG.  6T. 


CHAP,  in  THE   COMBUSTION   OF   GASES  135 

gas  lasting  for  1 J  hours,  and  is  then  allowed  to  stand 
for  12  hours.  If  inside  of  2-i  hours  never  more  than 
40  ccm.  of  the  gas  be  taken  for  analysis,  one  may  be 
sure  that  only  pure  oxyhydrogen  gas  is  being  em- 
ployed. To  take  off  a  portion  of  the  gas,  the  deliv- 
ery tube  is  brought  into  the  measuring  bulb,  and  by 
further  evolution  of  the  oxyhydrogen  gas  the  desired 
amount  of  the  same  is  driven  over.  The  freshly 
evolved  gas  containing  ozone  drives  the  pure  gas 
before  it.  Two  little  glass  cups,  d  and  e,  serve  as 
pole  contacts.  The  gas  is  set  free  by  the  plates  /. 
A  little  mercury  in  the  delivery  tube  at  b  closes  the 
apparatus  air-tight. 

THE  DIP  BATTERY 

For  producing  the  electric  current,  the  form  of 
dip  battery  devised  by  Bunsen  is  very  convenient 
(Fig.  68). 

In  this  form  the  zinc  and  carbon  plates  stand 
opposite  one  another,  and  are  dipped  into  a  single 
solution  which  is  prepared  as  follows : l  765  g.  of 
commercial  pulverised  potassium  bichromate,  which 
usually  contains  about  3  per  cent  of  impurities,  is 
gradually  brought  into  0.832  liter  of  sulphuric  acid 
of  1.836  sp.  gr.,  the  acid  being  constantly  stirred. 
When  the  potassium  bichromate  has  been  changed 
to  chromic  acid  and  potassium  sulphate,  9.2  liters  of 
water  is  poured  in,  in  a  thin  stream,  with  constant 
stirring.  The  mixture,  which  was  already  hot,  now 
heats  up  still  more,  and  the  crystals  gradually  dis- 
solve. 

1  PoggendorfP s  Annalen,  1875,  154,  248. 


136 


GAS  ANALYSIS 


PART    II 


The  above  amounts  make  10  liters  of  the  battery 
solution. 

If  the  circuit  be  closed  by  a  conductor  of  low 
resistance,  there  may  be  seen  in  the  red  solution  a 


FIG.  ti8. 


dark-coloured  column  of  liquid  which,  starting  from 
the  dissolving  zinc  plate,  sinks  to  the  bottom  and 
collects  in  the  lower  part  of  the  glass  cell  in  the 
form  of  a  rather  sharply  denned  layer. 


CHAP,  in  THE  COMBUSTION  OF  GASES  137 

The  original  solution  has  a  specific  gravity  of  1.140, 
while  that  charged  with  the  zinc  sulphate  has  a  spe- 
cific gravity  of  1.272.  Hence  the  liquid  once  used 
sinks  to  the  bottom  -and  is  constantly  replaced  by 
fresh,  unchanged  solution.  A  circulation  is  thus 
established  which  has  a  considerable  influence  upon 
the  constancy  of  the  current. 

THE  INDUCTION  COIL 

Sparks  for  the  explosion  are  best  obtained  by 
means  of  a  Ruhmkorff  inductor.  Too  small  a  coil 
should  not  be  chosen,  but  one  about  15  cm.  long  will 
be  found  sufficient.  If  the  induction  coil  is  too  small, 


it  may  easily  occur  that  the  spark  is  too  weak  to 
ignite  a  gas  mixture  which  is  but  slightly  explosive. 
The  author  would  further  recommend,  even  though 
in  hundreds  of  analyses  he  has  never  known  an  ex- 
plosion pipette  to  burst,  that  the  instrument  be  placed 
behind  a  screen  of  plate  glass  before  making  the 
explosion,  so  that  the  experimenter  may  surely  be 
protected  against  accident. 


138  GAS   ANALYSIS  PART  11 

THE  COMBUSTION  WITH  AN  ELECTRICALLY 
HEATED  PLATINUM  SPIRAL 

J.  Coquillion  was  the  first  to  propose  the  use  of  the 
glowing  platinum  spiral  in  the  determination  of  such 
gases  as  marsh-gas  and  hydrogen.  Clemens  Wink- 
ler  improved  the  form  of  the  apparatus  and  used 
a  Hempel  pipette  for  solid  and  liquid  reagents, 


FIG.  70. 


Fig.  32.  While  adhering  for  the  most  part  to  the 
Winkler  arrangement,  L.  M.  Dennis  has  lately  fur- 
ther improved  the  apparatus  so  far  as  the  process  of 
combustion  is  concerned,  by  arranging  it  for  use  with 
mercury  corresponding  to  the  mercury  pipettes  already 
described.  The  apparatus  is  shown  in  Fig.  70. 


CHAP,  in  THE   COMBUSTION  OF  GASES  139 

In  the  neck  of  the  pipette  is  inserted  a  single  bore 
rubber  stopper.  A  glass  tube  reaching  nearly  to  the 
top  of  the  pipette  passes  through  the  opening  of  the 
stopper.  Inside  of  the  glass  tube  is  a  stout  iron 
wire  which  projects  below  its  lower  end.  The  joint 
between  the  glass  tube  and  the  iron  wire  is  made 
air-tight  by  slipping  a  short  piece  of  thick-walled 
rubber  tubing  over  both  and  wiring  it  in  place. 
Another  piece  of  stout  iron  wire  is  pushed  up  through 
the  stopper  so  that  it  occupies  the  position  shown  in 
the  figure.  The  upper  ends  of  these  wires  are  joined 
by  a  spiral  of  platinum  wire  ^  mm.  in  diameter,  the 
coil  of  the  wire  being  about  2  mm.  in  diameter  and 
containing  from  20  to  30  turns.  This  spiral  is  bent 
into  the  form  of  a  horizontal. S.  The  lower  ends 
of  the  two  iron  wires  are  joined  to  two  insulated 
binding  posts,  as  shown  in  the  illustration. 

After  the  rubber  stopper  has  been  inserted  in  place, 
and  the  wires  have  been  connected  with  the  binding 
posts,  the  pipette  and  capillary  are  filled  with  mer- 
cury by  raising  the  level-bulb.  The  pinchcock  on 
the  rubber  tube  on  the  capillary  is  closed  and  the 
tube  of  the  level-bulb  is  connected  with  a  water 
suction  pump.  By  applying  suction  in  this  manner 
the  air  in  the  glass  tube  surrounding  the  one  iron 
wire  is  drawn  out  and  rises  to  the  top  of  the  pipette, 
the  tube  becoming  completely  filled  with  mercury. 

Winkler  mixed  with  air  the  gas  which  is  to  be 
burned  and  then  allowed  this  mixture  to  flow  slowly 
through  a  burette  into  the  combustion  pipette  against 
the  glowing  platinum  spiral.  Dennis,  on  the  other 
hand,  brings  into  the  pipette  the  total  amount  of  the 
gas  which  is  to  be  burned,  and  then  introduces  into 


140  GAS  ANALYSIS  PART  n 

the  burette  a  volume  of  oxygen  which  is  more  than 
sufficient  for  the  combustion,  and  notes  this  volume. 
He  then  joins  the  burette  with  the  pipette  in  the  usual 
manner  by  means  of  a  bent  capillary  tube,  heats  the 
platinum  spiral  to  glowing,  and  then  with  the  spiral 
still  glowing  slowly  passes  oxygen  over  into  the 
combustion  pipette.  The  chief,  advantages  of  this 
procedure  are  :  first,  the  use  of  a  large  volume  of 
combustible  gas  and  consequent  increase  in  the  ac- 
curacy of  the  work ;  second,  the  avoidance  of  explo- 
sion by  the  gradual  addition  of  oxygen ;  and  third, 
the  avoidance  of  the  formation  of  oxides  of  nitrogen 
in  the  combustion  of  all  such  gas  mixtures  as  contain 
little  or  none  of  this  gas  because  of  the  addition  of 
pure  oxygen  instead  of  air. 

THE  COMBUSTION  WITH  A  PLATINUM 
CAPILLARY  TUBE 

The  two  methods  just  described  necessitate  the 
use  of  an  electric  current.  The  combustion  can  also 
be  effected  by  means  of  a  platinum  capillary  tube 
heated  from  without  with  a  flame,  provided  that  this 
flame  generates  only  just  enough  heat  to  bring  the 
capillary  to  glowing.  Orsat  had  already  stated  that 
it  must  be  possible  to  burn  methane  by  means  of  a 
heated  capillary  platinum  tube,  but  the  actual  solu- 
tion of  this  problem  is  original  with  H.  Drehschmidt. 
The  capillary  tube  used  by  Drehschmidt  consists  of 
a  platinum  tube  200  mm.  long,  2  mm.  external 
diameter,  and  0.7  mm.  internal  diameter.  To  both 
ends  of  this  tube  are  soldered  large  pieces  of  brass 
tubing.  To  avoid  explosions,  the  internal  space  of 


CHAP.     Ill 


THE   COMBUSTION  OF   GASES 


141 


the  capillary  is  filled  throughout  its  entire  length 
'with  three  or  four  fine  platinum  wires. 

Clemens  Winkler  has  markedly  improved  this 
combustion  capillary  by  providing  both  ends  of  it 
with  small  water  coolers,  and  in  this  way  has  reduced 
its  length  to  100  mm. 

The  arrangement  which  the  author  uses  in  his 
laboratory  is  shown  in  Fig.  71.  A  platinum  tube 


Fio.  71. 

100  mm.  long,  and  made  according  to  the  directions 
of  Drehschmidt  and  Winkler,  lies  between  the  two 
cooling  tubes  a  and  b.  These  tubes  are  of  brass, 
closed  at  the  lower  end,  and  are  about  15  mm.  wide 
and  80  mm.  long.  The  platinum  tube  is  soldered  to 
copper  tubes  about  3J  mm.  wide  and  bent  downward 


142  GAS   ANALYSIS  PART  n 

at  right  angles.  The  contact  between  the  copper  and 
the  capillary  lies  within  the  cooling  tube.  The  whole 
apparatus  is  supported  by  two  iron  rods  c  and  <?, 
which  are  notched  at  the  top.  To  keep  the  heat  of 
the  flame  away  from  the  cooling  tubes  as  much  as 
possible,  a  little  box  of  asbestos,  open  below  and 
provided  with  an  opening  in  its  cover,  is  placed  over 
the  platinum  capillary.  The  propagation  of  the 
combustion  from  the  capillary  into  the  combustible 
mixture  in  the  burette  or  pipette  is  made  impossi- 
ble by  the  insertion  of  platinum  wires  into  the  bent 
copper  tubes.  If  there  are  used  for  this  purpose 
short  pieces  of  platinum  wire  which  fill  the  interior 
space  of  the  copper  tubes  almost  completely,  a  highly 
explosive  gas  mixture  may  be  burned  without  danger 
of  the  combustion  proceeding  from  the  tubes  and 
causing  an  explosion  in  the  burette  or  pipette. 
When  an  analysis  is  being  made,  the  brass  cooling 
tubes  a  and  b  are  filled  with  water.  It  is  not  really 
necessary  to  fill  the  platinum  tube  also  with  platinum 
wires  for  the  sake  of  avoiding  an  explosion,  since  the 
arrangement  which  has  just  been  described  cools  the 
gases  so  strongly  that  all  gas  mixtures  are  brought 
below  their  kindling  temperature,  but  it  is  never- 
theless desirable  to  fill  the  platinum  tube  with  plati- 
num wires,  so  that  the  internal  space  of  the  former 
may  be  lessened  as  much  as  possible. 

To  burn  a  gas  with  this  apparatus,  transfer  it 
first  to  the  mercury  pipette  B  and  close  this  with 
the  pinchcock.  Then  measure  off  in  a  burette  a 
volume  of  air  or  oxygen  that  is  surely  sufficient  to 
burn  the  combustible  constituents  of  the  gas  mix- 
ture. Connect  the  combustion  capillary  with  the 


CHAP,  in  THE   COMBUSTION   OF   GASES  143 

burette  and  pipette  in  the  manner  shown  in  the 
figure,  and  heat  the  tube  to  bright  redness  by  means 
of  a  flame.  Drive  the  gases  back  and  forth  through 
the  capillary  by  raising  and  lowering  the  level-bulb 
until  complete  combustion  has  taken  place. 

A  further  advantage  of  this  capillary  lies  in  the 
fact  that  it  so  reduces  the  temperature  of  the  gases 
which  pass  through  it  that  the  combustion  tempera- 
ture of  nitrogen  cannot  be  reached. 

The  platinum  capillary  is  undoubtedly  the  sim- 
plest form  of  combustion  apparatus  for  technical  pur- 
poses. Perfectly  reliable  results  are  given  by  all 
three  methods  —  that  is,  the  combustion  in  the  plati- 
num capillary,  the  explosion  with  air,  and  combus- 
tion in  the  combustion  pipette  with  oxygen.  The 
accuracy  of  the  results  is  in  all  cases  increased  if  the 
analyses  are  made  with  apparatus  that  is  filled  with 
mercury,  and  that  permits  of  correction  for  variations 
in  temperature  and  pressure. 


CHAPTER   IV 

PARTICULARS   CONCERNING   THE 
DETERMINATIONS   OF   THE   VARIOUS   GASES 

To  obtain  accurate  analytical  results,  it  is  of  the 
greatest  importance  to  know  exactly  the  absorbing 
power  possessed  by  the  reagents  when  manipulated  in 
the  pipettes  in  the  manner  already  described.  For 
this  reason  the  author  has  determined  this  absorbing 
power,  his  idea  here  being  that  it  is  not  so  important 
to  know  how  much  of  a  gas  an  absorbent  may  be 
able  to  take  up  under  the  most  favourable  circum- 
stances, but  rather  to  ascertain  how  much  it  can 
absorb  with  a  certain  rapidity,  so  that,  in  spite  of  the 
short  duration  of  the  absorption  in  the  pipettes,  the 
completeness  of  this  absorption  is  guaranteed. 

For  this  purpose  a  pipette  with  a  very  fine  capil- 
lary tube  (Fig.  47)  was  filled  with  mercury  and 
1  ccm.  of  the  reagent.  The  accurately  measured  re- 
agent is  here  confined  between  two  columns  of  mer- 
cury, and  is  thus  completely  protected  from  the  air. 
The  pipette  was*  then  connected,  by  means  of  a  piece 
of  rubber  tubing  and  a  capillary  tube,  with  a  simple 
gas  burette  containing  the  gas  under  consideration. 
This  gas  was  next  drawn  into  the  pipette  and  shaken 
as  long  as  a  rapid  absorption  took  place,  several  cubic 
centimeters  at  the  least  disappearing  in  the  space  of 

144 


CHAP,  iv  DETERMINATION  OF   OXYGEN  145 

one  minute.  Since  the  figures  thus  experimentally 
determined  give  to  the  reagent  an  absorbing  power 
much  higher  than  that  which  could  be  relied  upon  in 
an  analysis,  they  are  divided  by  four,  under  the  pre- 
sumption that  only  a  fourth  of  the  reagent  should  be 
used  if  there  is  to  be  no  doubt  as  to  its  absorbing 
power. 

Accordingly,  1  ccm.  of  approximately  33J  per 
cant  caustic  potash  solution  can  absorb  not  merely 
40  ccm.  of  carbon  dioxide,  as  is  stated  later,  but  really 
160  ccm.  The  figures  thus  obtained  will  be  desig- 
nated as  the  "  analytical  absorbing  power  " ;  they 
refer  to  1  ccm.  of  the  reagent. 

If  an  accurate  account  is  kept  of  how  much  gas  the 
pipette  has  absorbed,  the  effectiveness  of  the  reagent 
remaining  in  the  pipette  is  always  known,  and  full 
use  of  the  absorbent  can  be  made  without  bringing 
the  accuracy  of  the  analysis  in  question. 

OXYGEN 

Specific  gravity,  1.10521  *;  weight  of  1  liter, 
1.43003;  critical  temperature,  —118°;  critical  press- 
ure, 50  atmospheres.  Boiling-point  under  one  atmos- 
phere pressure,  — 181.4°  ;  specific  gravity  of  liquid 
oxygen  s  =  1.124. 

Oxygen  is  but  slightly  soluble  in  water.  One  liter 
of  water  absorbs,  from  atmospheric  air,  according  to 
L.  W.  Winkler,2  Otto  Pettersson,  and  K.  Sonden3  at 
760  mm.  pressure  :  — 

1  Most  of  these  figures  are  from  Landolt  and  Bernstein's  Physik- 
alisch-chemische  Tabellen.    The  liter  weights  are  referred  to  Berlin. 

2  Berichte  der  deutschen  chemischen  G-esellschaft,  21,  p.  2843. 

3  Ibid.,  1889,  p.  1443. 


146  GAS  ANALYSIS  PART  n 

At  0°C.  10.01  com. 

"  6°  C.  8.3  « 

"  9.18°  C.  7.9  " 

"  14.1°    C.  7.05  " 

"  16.87°  C.  6.84  « 

"  23.64°  C.  5.99  " 

"  24.24°  C.  5.916  " 

and  of  pure  oxygen,  according  to  Bunsen  — 
At  20°  C.,  28.38  com. 

One  volume  of  alcohol  absorbs,  according  to  Carius, 
at  all  temperatures  between  0°  and  24°,  0.28397  volume. 

Molten  metals  take  up  oxygen  with  avidity.  Ac- 
cording to  Levol,1  silver  in  the  fluid  condition  absorbs 
about  ten  times  its  volume  of  oxygen  and  gives  it  up, 
with  foaming,  when  gold  is  added;  it  also  gives  it 
up  on  simply  solidifying,  the  so-called  "  spitting  "  of 
silver.  If  silver,  melted  with  access  of  oxygen,  be 
dropped  into  water,  large  bubbles  of  oxygen  are  given 
off  by  each  drop.  Cobalt  and  nickel  act  similarly. 

Oxygen  is  determined  either  by  combustion  with 
an  excess  of  hydrogen  or  copper,  or  by  absorption. 

The  combustion  may  be  carried  out  with  any  one 
of  the  forms  of  apparatus  described  on  pp.  130  to  143. 

In  the  combustion  with  hydrogen,  f  of  the  volume 
burned  consists  of  hydrogen,  and  J  of  oxygen.  The 
volume  of  oxygen  present  is  hence  found  by  dividing 
by  three  the  decrease  in  volume  resulting  from  the 
combustion. 

The  necessary  hydrogen  may  be  made  in  the 
apparatus  described  on  pp.  131  and  133. 

1  Cl.  Winkler,  Anleitung  zur  Untersuchung  der  Industrie-Gase, 
Part  I,  p.  83. 


CHAP,  iv  DETERMINATION  OF   OXYGEN  147 

To  obtain  the  greatest  accuracy,  Bunsen  uses  hydro- 
gen produced  by  the  electrolysis  of  water,  the  positive 
pole  consisting  of  a  zinc  wire  floating  in  mercury.1 

If  the  explosion  pipette  is  to  be  used  for  the  com- 
bustion, pure  oxygen  may  be  burned  according  to 
Bunsen's  procedure  by  mixing  it  with  from  three  to 
ten  times  its  volume  of  hydrogen.  If  larger  amounts 
are  added,  the  inflammability  is  destroyed,  or  what 
is  more  to  be  feared,  is  partially  obstructed.  If  the 
gas  is  poor  in  oxygen,  it  is  mixed  with  twice  its 
amount  of  hydrogen  ;  and  if  the  mixture  is  still  not 
inflammable,  electrolytic  oxyhydrogen  gas  is  added 
until  complete  combustibility  is  established.  The 
gases  should  always  be  vigorously  shaken  in  the 
explosion  pipette  before  the  combustion. 

To  make  sure  that  the  combustion  has  not  taken 
place  near  the  limit  of  inflammability,  the  experiment 
must  be  repeated  with  a  somewhat  larger  amount  of 
oxyhydrogen  gas. 

If  the  two  experiments  do  not  agree,  then  only 
that  one  made  with  the  larger  amount  of  combustible 
gas  is  to  be  regarded  as  correct.  With  some  experi- 
ence, however,  one  can  easily  tell  from  the  strength 
of  the  explosion  whether  the  proportion  of  combustible 
to  incombustible  gas  was  such  that  a  complete  com- 
bustion must  have  taken  place. 

Morley  in  his  admirable  researches  upon  the  com- 
position of  water  has  carried  on  combustions  of  hydro- 
gen with  oxygen  with  a  high  degree  of  accuracy. 

Very  accurate  determinations  of  oxygen  may  be 
made  by  combustion  with  copper.  U.  G.  Kreusler 
has  so  improved  the  apparatus  devised  by  Ph.  v.  Jolly 

1  Bimsen,  Gasometrische  Methoden,  2d  ed.  p.  80. 


148  GAS  ANALYSIS  PART  n 

for  the  determination  of  oxygen  in  the  atmosphere 
that  it  is  now  one  of  the  most  exact  methods  known. 
A  so-called  copper  eudiometer,  whose  construction  is 
based  upon  his  well-known  air  thermometer,  is  used 
for  the  determination.  The  air  whose  oxygen  con- 
tents is  to  be  determined  is  admitted  into  a  bulb 
which  has  previously  been  completely  exhausted,  and 
the  pressure  is  read  off  on  a  very  exact  mercury 
manometer.  The  oxygen  is  then  absorbed  by  a 
copper  spiral  that  is  heated  to  glowing  by  a  strong 
electric  current ;  the  metallic  copper  is  changed  to 
cuprous  and  cupric  oxide.  After  the  apparatus  has 
become  perfectly  cool,  the  remaining  nitrogen  is 
brought  to  the  initial  volume  by  changing  the 
pressure,  and  a  reading  is  taken  of  the  pressure  now 
prevailing.1  When  due  regard  is  given  to  all  the 
necessary  precautions,  the  method  is  of  the  greatest 
exactness ;  it  is,  however,  very  complex  and  tedious, 
and  for  this  reason  is  not  well  suited  to  the  making 
of  a  large  number  of  determinations. 

When  oxygen  is  mixed  with  combustible  gases  it  is 
necessary  to  determine  it  by  absorption. 

With  absorbents  a  very  rapid  and,  with  the  use  of 
the  necessary  precautions,  a  very  accurate  determi- 
nation of  oxygen  may  be  made.  Good  absorbents  for 
oxygen  are  — 

1.  A  strongly  alkaline  solution  of  pyrogallol. 

2.  Chromous  chloride. 

3.  Phosphorus. 

4.  Metallic  copper. 

1  U.  Kreusler,  Ueber  den  Sauerstoffgehalt  der  atmospharischen 
Luft.  Landwirthschaftliche  Jqhrbucher,  1885,  p.  305, 


CHAP,  iv  DETERMINATION  OF   OXYGEN  149 

1.    Alkaline  Pyrogallol 

The  alkaline  solution  of  pyrogallol  is  prepared  by 
mixing  together,  either  directly  in  the  absorption 
pipette  or  in  the  apparatus  to  be  described  later,  5  gr. 
of  pyrogallol  dissolved  in  15  ccm.  of  water,  and  120  g. 
of  potassium  hydroxide  dissolved  in  80  ccm.  of  water. 

Especial  attention  must  be  called  to  the  fact  that 
caustic  potash  purified  with  alcohol  should  not  be 
used,  since  this  preparation,  even  after  quite  strong 
ignition,  may  cause  erroneous  results  in  the  analysis. 

The  absorptions  should  not  be  carried  on  at  a 
temperature  under  15°,  for  it  has  been  observed  that 
the  alkaline  pyrogallol  used  for  absorption  is  very 
much  less  active  at  a  temperature  under  7°.  At  a 
temperature  of  15°  or  higher,  the  last  trace  of  oxygen 
can  be  removed  with  certainty  in  the  space  of  three 
minutes  by  shaking  with  the  solution  of  alkaline 
pyrogallol,  while  at  lower  temperatures  the  absorp- 
tion was  not  complete  after  six  minutes ;  moreover, 
the  liquid  began  to  foam,  and  this,  in  exact  determi- 
nations, is  very  troublesome. 

A  solution  prepared  as  above  gave  off  no  carbon 
monoxide  during  the  absorption,  or  at  the  most  only 
such  slight  traces  that  the  error  thus  caused  came 
within  the  limit  of  error  of  the  readings. 

To  ascertain  how  great  the  error  is  which  can  be 
caused  by  the  evolution  of  carbon  monoxide,  the 
author's  assistant,  Herr  Oettel,  in  Dresden,  and 
Herren  Kreusler  and  Tacke,  in  Bonn,  analysed  sam- 
ples of  air  which  were  collected  by  Kreusler  in  Bonn, 
and  sent  to  Dresden  in  bulbs  sealed  by  fusion. 

The  results  were  as  follows  :  — 


l! 


+ +   + 


I 
++ 


11      1 


+4-  + 

I- 


88 


,f ' 

H,O  ^         COiH 


§> 


8 


r 


88 


88 


I 


I 


CHAP,  iv  DETERMINATION  OF   OXYGEN  151 

These  results  show  that  determinations  made  with 
the  copper  eudiometer  differ  from  one  another  by  two 
to  three  hundredths  of  a  per  cent ;  the  same  is  also 
true  of  the  analyses  made  with  the  hydrogen  eudi- 
ometer. The  pyrogallol  method  is  the  most  rapid 
and  gives  the  best  agreeing  results,  so  that  it 
appears  to  be  especially  suited  for  parallel  analyses. 

In  technical  analysis  this  solution  is  used  in  the 
double  pipette  (Fig.  33)  ;  in  exact  analysis  in  an 
ordinary  pipette  (Fig.  47).  To  effect  the  absorp- 
tion, the  gas  is  shaken  for  three  minutes  with  the 
solution.  The  absorption  proceeds  somewhat  slowly 
and  for  this  reason  the  pipette  shown  in  Fig.  34 
cannot  be  used.  To  obtain  accurate  results  a  shak- 
ing of  three  minutes  is  absolutely  necessary.  The 
analytical  absorbing  power  of  the  solution  is  from 
2  to  2|. 

If  a  large  number  of  oxygen  determinations  are  to 
be  made  by  the  "  exact "  method,  the  reagent  is  kept 
in  the  apparatus  shown  in  Fig.  72.  With  this  ap- 
paratus a  large  quantity  of  the  reagent  may  be  kept, 
measured  off,  and  transferred  to  the  absorption 
pipettes  without  ever  coming  in  contact  with  the 
air. 

The  large  reservoir  bulb  A  ends  above  in  the  U- 
shaped  tube  B,  which  has  a  short  side-arm  at  /  and 
ends  in  the  I-  -shaped  capillary  </.  To  the  lower  side 
of  the  bulb  is  attached  the  bent  tube  A,  which  is 
provided  with  a  glass  stopcock  i.  A  small  funnel 
can  be  fastened  to  the  upper  end  of  h  by  a  rubber 
tube  k.  A  thin  rubber  tube  connects  the  side-arm 
/  with  the  funnel  o.  The  ends  of  the  H-  capillary  g 
are  provided  with  short  pieces  of  rubber  tubing  and 


152  GAS   ANALYSIS  PART  n 

with  pinchcocks.  The  apparatus  is  first  filled  com- 
pletely with  mercury.  A  funnel  or  glass  tube  is  then 
inserted  in  the  free  end  of  m,  the  pinchcocks  n  and  y 
are  closed,  the  stopcock  i  is  opened,  and  the  aqueous 
solution  of  pyrogallol  is  poured  into  the  funnel 
attached  to  m.  The  end  k  of  the  tube  h  is  now 
connected  by  a  rubber  tube  with  a  suction  flask, 
and  the  flask  is  joined  to  an  aspirator.  Upon  open- 
ing the  pinchcock  at  m  the  mercury  flows  through  h 
into  the  flask,  and  the  solution  of  pyrogallol  is  drawn 
into  A.  The  entrance  of  the  reagent  can  be  instantly 
stopped  by  turning  the  stopcock  i.  When  all  of  the 
pyrogallol  has  entered  the  pipette,  the  solution  of 
potassium  hydroxide  is  poured  into  the  funnel  and 
drawn  in  in  the  same  manner.  The  two  solutions 
in  the  apparatus  are  then  thoroughly  mixed  by 
shaking. 

To  transfer  some  of  the  reagent  to  a  pipette,  the 
apparatus  is  arranged  as  shown  in  Fig.  72.  The 
capillary  of  the  pipette  is  inserted  at  y  into  the  end 
of  the  rubber  tube  attached  to  the  lower  end  of  g. 
By  blowing  into  I  (this  can  be  best  done  with  the 
rubber  pump,  Fig.  17)  the  mercury  in  the  pipette  is 
driven  to  #,  and  w,  ^,  and  y  are  then  closed.  Some 
mercury  is  poured  into  the  funnel  inserted  in  &,  and 
i  is  opened.  Upon  lowering  the  funnel  o  and  open- 
ing the  pinchcock  w,  the  left  side  of  the  U-shaped 
tube  B  can  easily  be  filled  down  to  a  mark  with  the 
reagent,  for  the  mercury  drives  the  reagent  out  of 
the  bulb  into  B.  When  the  reagent  has  been  thus 
measured  off,  i  is  closed,  y  is  opened,  and  by  raising 
the  funnel  o  the  reagent  is  driven  over  into  the  pipette 
until  the  mercury  reaches  the  point  x.  The  pipette 


DETERMINATION  OF   OXYGEN 


153 


is  then  disconnected,  the  capillary  d  is  immersed  in 
a  beaker  of  distilled  water,  and  by  careful  alternate 
sucking  and  blowing  at  I  the  capillary  is  freed  within 


Fm.  72. 


and  without  from  the  last  traces  of  the  reagent.  It 
is  then  dried  with  filter  paper,  and  the  pipette  is 
ready  for  use. 


154  GAS   ANALYSIS  PAHI  n 

2.    Chromous  Chloride 

Chromous  chloride  also  may  be  used  for  absorbing 
oxygen.1  The  fact  that  this  reaction  is  not  influenced 
by  hydrogen  sulphide  or  carbon  dioxide  is  further  a 
great  advantage.  These  two  gases  are  completely 
indifferent  to  both  the  blue  chromic  chloride  and 
the  green  chromous  chloride  solutions. 

Chromous  chloride  is  the  only  absorbent  that  will 
absorb  the  oxygen  alone  in  a  mixture  of  oxygen  and 
hydrogen  sulphide. 

To  prepare  chromous  chloride,  Von  der  Pfordten 
has  used  the  method  given  by  Moissan.  A  green 
solution  of  chromic  chloride  free  from  chlorine  is 
made  by  heating  chromic  acid  with  concentrated 
hydrochloric  acid,  and  this  solution  is  then  reduced 
with  zinc  and  hydrochloric  acid.  Since  spongy  par- 
ticles always  separate  from  the  zinc  used  for  the 
reduction,  the  solution  must  be  filtered.  For  this 
purpose  the  reduction  is  carried  on  in  a  flask  fitted 
with  a  long  and  a  short  tube,  as  is  a  wash-bottle. 
The  longer  tube  is  bent  downward  above  the  flask 
and  is  here  supplied  with  a  small  bulb-tube,  which  is 
filled  with  glass-wool  or  asbestos.  The  hydrogen 
given  off  during  the  reduction  is  allowed  to  pass  out 
through  the  longer  tube  for  some  time ;  then  after 
closing  its  outer  end  the  tube  is  pushed  down  into 
the  solution.  The  hydrogen  is  thus  obliged  to  pass 
out  through  the  shorter  tube,  which  carries  a  rubber 
valve.  Carbon  dioxide  is  then  passed  into  the  flask 
through  the  short  tube,  and  the  chromous  chloride 

i  Otto  von  der  Pfordten,  Liebig's  Annalen,  228,  112. 


CHAP,   iv  DETERMINATION   OF   OXYGEN  155 

solution  is  driven  over  into  a  beaker  containing  a 
saturated  solution  of  sodium  acetate ;  a  red  precipi- 
tate of  chromium  acetate  is  formed  which  is  washed 
Dy  decantation  with  water  containing  carbonic  acid. 
The  red  chromium  acetate  is,  relatively  speaking, 
quite  unchangeable,  and  in  moist  condition  it  may 
be  kept  for  an  unlimited  time  in  closed  bottles  filled 
with  carbon  dioxide. 

In  washing  the  red  precipitate,  some  free  acetic 
acid  is  added  in  the  beginning,  to  dissolve  an}^  basic 
zinc  carbonate  which  may  have  been  thrown  down. 
In  this  way  a  preparation  completely  free  from  zinc 
is  obtained. 

To  absorb  oxygen,  the  chromium  acetate  is  decom- 
posed by  the  addition  of  hydrochloric  acid,  the  air 
being  excluded.  L;  k;  advisable  to  use  an  excess  of 
chromium  acetate  in  order  to  avoid  the  presence  of 
free  hydrochloric  acid. 

3.   Phosphorus 

The  absorption  of  oxygen  with  phosphorus,  as 
described  by  Lindemann,  is  much  more  convenient 
than  the  two  preceding  methods.  To  obtain  the 
phosphorus  in  the  necessary  stick  form,  it  is  melted 
under  water  in  a  test-tube  placed  in  a  water  bath, 
the  temperature  of  the  water  being  about  50°. 
Enough  phosphorus  is  used  to  form  a  column  about 
6  cm.  high.  A  slightly  conical  glass  tube  of  2  to  3 
mm.  internal  diameter  is  then  dipped  into  the  molten 
phosphorus,  the  upper  end  of  the  tube  is  closed  with 
the  finger,  and  the  tube  is  lifted  out  and  dipped  im- 
mediately into  a  tall  beaker  full  of  water.  A  peculiar 


156  GAS   ANALYSIS  PART  n 

movement  takes  place  in  the  phosphorus  enclosed  in 
the  tube  at  the  moment  when  it  solidifies,  and  since 
the  phosphorus  undergoes  a  marked  decrease  of  vol- 
ume when  it  becomes  solid,  the  stick  usually  falls 
out  of  the  tube  upon  gentle  tapping ;  if  it  adheres,  it 
can  easily  be  pushed  out  with  a  wire. 

These  phosphorus  sticks  are  used  in  the  absorption 
pipette  for  solid  and  liquid  reagents  (Fig.  32)  ;  the 
cylindrical  part  is  filled  as  full  as  possible  with  the 
sticks,  the  remaining  space  being  filled  with  distilled 
water. 

To  make  the  absorption,  the  gas  whose  oxygen 
contents  is  to  be  determined  is  driven  over  into  the 
pipette,  thereby  displacing  the  water  and  coming 
into  contact  with  the  moist  sticks  of  phosphorus.  A 
bright  glow  is  visible  when  the  reaction  proceeds 
normally  ;  the  phosphorus  burns  to  phosphoric  acid, 
phosphorus  acid,  etc.,  at  the  expense  of  the  oxygen. 
After  three  minutes,  at  the  longest,  the  absorption 
is  complete.  The  end  of  the  absorption  is  sharply 
shown  by  the  disappearance  of  the  glow  when  the 
pipette  is  in  a  dark  room. 

Since  the  different  oxidation  products  of  phos- 
phorus are  all  soluble  in  water,  the  surface  of  the 
sticks  of  phosphorus  is  kept  fresh  by  the  action  of 
the  confining  water  alone,  if  that  be  renewed  from 
time  to  time.  And  further,  since  these  oxidation 
products,  as  solid  and  liquid  substances,  have  a  very 
small  tension,  no  error  is  caused  by  the  white  cloud 
which  may  be  present  in  the  gas  residue  after  the 
absorption.  The  phosphorus  can  of  course  be  used 
for  a  very  large  number  of  analyses,  if  it  is  protected 
from  the  action  of  the  light.  To  do  this  the  cylin- 


CHAP,  iv  DETERMINATION  OF  OXYGEN  157 

drical  part  of  the  pipette  is  covered  with  a  small  box, 
or  the  whole  pipette  is  covered,  when  not  in  use,  by 
a  light-tight  box  of  wood  or  cardboard. 

Parallel  analyses  showed  that  the  absorption  with 
phosphorus  is  very  complete,  and  hence  this  Linde- 
mann  process  for  the  determination  of  oxygen  must 
be  classed  among  the  finest  of  gas  analytic  methods, 
it  being  of  especial  value  because  with  one  filling  of 
the  pipette  enormous  quantities  of  oxygen  may  be 
absorbed,  while  alkaline  pyrogallol  possesses  a  rela- 
tively small  absorbing  power. 

Naturally  the  method  cannot  be  used  under  those 
conditions  in  which  phosphorus  is  no  longer  able  to 
unite  with  oxygen.  Detailed  experiments  have  been 
made  upon  this  point  by  Schonbein  in  his  researches 
upon  ozone.  He  states  that  the  reaction  is  entirely 
or  partly  prevented  by  the  presence  of  ethylene  (^^ 
volume  of  ethylene  is  sufficient)  and  other  hydrocar- 
bons or  ethereal  oils,  alcohol,  and  traces  of  ammonia. 

Moreover,  oxygen  does  not  act  upon  phosphorus 
when  the  gas  has  a  very  large  partial  pressure.  If 
phosphorus  be  brought  into  contact  with  oxygen  of 
the  density  of  the  atmosphere,  no  reaction  whatever 
takes  place,  and  not  the  least  light  is  seen.  If,  how- 
ever, the  oxygen  be  diluted  with  another  gas,  or 
mechanically  by  the  air-pump,  the  reaction  begins 
when  the  gas  has  been  brought  to  about  75  per  cent 
of  its  initial  partial  pressure.  At  first  a  feeble  glow 
is  seen  and  then  suddenly,  with  a  sort  of  explosive 
flash  of  light,  the  oxygen  burns,  the  phosphorus 
being  partly  melted. 

The  reaction  takes  place  normally  in  gases  which 
do  not  contain  more  than  50  per  cent  of  oxygen. 


158  GAS  ANALYSIS  PART  n 

To  investigate  gases  which  are  rich  in  oxygen,  it  is 
advisable  to  dilute  them  with  an  equal  volume  of 
nitrogen  made  from  air  by  absorbing  the  oxygen 
with  phosphorus.  Mixtures  of  oxyhydrogen  gas  and 
air  even  when  highly  diluted  may  become  so  strongly 
heated  as  to  cause  an  explosion. 

The  reaction  is  further  dependent  upon  the  tem- 
perature. 

It  proceeds  normally  at  about  20°  C.,  while  at  14° 
it  takes  place  quite  slowly,  so  that  a  quarter  of  an 
hour  or  longer  is  required  to  completely  separate  the 
oxygen  from  100  ccm.  of  air.  At  10°  and  still  lower 
temperatures  a  half  hour's  time  would  not  be  sufficient. 
It  follows  from  this  that  during  the  colder  months 
of  the  year  the  absorption  must  be  carried  out  in 
warmed  rooms. 

4.    Copper 

Copper  at  a  red  heat  or  at  ordinary  temperatures 
may  be  used  for  the  absorption  of  oxygen. 

The  method  of  Jolly,  in  which  a  copper  wire  is 
electrically  heated  to  glowing,  has  been  mentioned 
above.  Copper  powder  made  by  reducing  granular 
copper  oxide  with  hydrogen  may  also  be  employed. 
If  a  hard  glass  tube,  filled  with  this  powder,  be  heated 
to  red  heat  in  a  combustion  furnace  and  the  gases  be 
then  led  through  the  tube,  they  can  in  this  manner 
be  completely  freed  from  oxygen. 

A  very  active  absorbent  for  oxygen  is  metallic 
copper  in  the  form  of  little  rolls  of  wire-gauze, 
immersed  in  a  solution  of  ammonia  and  ammonium 
carbonate. 

It  has  long  been  known  that  many  metals  oxidise 


CHAP,  iv  DETERMINATION   OF   OXYGEN  159 

readily  in*  the  presence  of  vapour  of  ammonia.  The 
absorption  of  oxygen,  however,  takes  place  rapidly 
only  so  long  as  the  metallic  surface  is  bright,  and  it 
proceeds  very  slowly  as  soon  as  considerable  quantities 
of  oxide  are  formed. 

By  the  admirable  researches  which  C.  Schnabel 
has  made  upon  the  solubility  of  the  oxides  of  zinc, 
copper,  etc.,  in  ammonium  carbonate,  in  connection 
with  his  work  upon  the  desilverisation  of  lead  by 
zinc,1  the  author  was  led  to  make  experiments  to  see 
whether  it  might  not  be  possible  to  effect  a  complete 
absorption  by  using  ammonium  carbonate  as  a  solvent 
for  the  oxides  formed.  Experiments  showed  that 
oxygen  is  completely  and  quickly  absorbed  when 
brought  into  contact  with  copper  and  a  solution  of 
commercial  ammonium  carbonate,  but  that  at  the 
same  time  not  inconsiderable  quantities  of  carbon 
dioxide  are  given  off.  When  zinc  was  used,  a  simul- 
taneous evolution  of  hydrogen  took  place,  and  iron 
proved  to  be  very  slow  in  its  action,  as  was  to  be 
expected  from  the  insolubility  of  its  oxide.  Further 
experiment  showed  that  a  very  rapid  and  complete 
absorption  of  oxygen  results,  without  any  other  gas 
being  at  the  same  time  given  off,  when  the  oxygen 
is  brought  into  contact  with  metallic  copper  and  a 
solution  consisting  of  equal  parts  of  a  saturated 
solution  of  pieces  of  commercial  ammonium  sesqui- 
carbonate,  and  a  solution  of  ammonia  of  0.93  specific 
gravity.  Such  an  ammoniacal  solution  has  a  tension 
which  may  in  most  cases  be  disregarded,  and,  provided 
that  the  absorption  apparatus  contains  sufficient 

1  Zeitschrift  fur  das  Berg-,  Hutten-  und  Salinenwesen  im  preus* 
sischen  Staaie,  28. 


160  GAS   ANALYSIS  PART  n 

metallic  copper,  the  solution  can  easily  absorb  24 
times  its  volume  of  oxygen.  Hence  its  analytical 
absorbing  power  is  6.  Since  the  surface  of  metallic 
copper  is  frequently  covered  with  a  thin  layer  of 
grease,  it  is  necessary  to  clean  it  before  using  by  ex- 
posing it  for  a  moment  to  the  action  of  nitric  acid. 

The  reagent  is  used  in  the  same  manner  as  phos- 
phorus, in  a  pipette  for  solid  absorbents.  In  making 
the  absorption,  the  gas  is  allowed  to  remain  in  the 
pipette  for  five  minutes. 

The  method  described  admits  of  a  very  rapid  and 
exact  determination  of  oxygen,  and  is  to  be  preferred 
to  the  ordinary  methods  with  alkaline  pyrogallol 
and  phosphorus,  provided  that  the  gases  do  not  con- 
tain carbon  monoxide.  As  compared  with  alkaline 
pyrogallol,  copper  has  a  much  greater  absorbing 
power  for  oxygen,  and  it  has  the  advantage  over 
phosphorus,  aside  from  the  danger  attending  the 
use  of  the  latter,  of  absorbing  equally  well  at  any 
temperature,  while  the  absorption  of  oxygen  by 
phosphorus  takes  place  very  slowly  at  temperatures 
below  14°  C.  Direct  experiments  showed  that,  at  a 
temperature  of  —7°  C.,  the  absorption  of  oxygen  in 
the  air  was  complete  in  five  minutes. 

In  the  analysis  of  gas  mixtures  which  contain 
carbon  monoxide  the  method  cannot  be  used,  because 
the  basic  ammonium  cuprous  carbonate,  formed  from 
the  copper  present,  absorbs  carbon  monoxide. 

The  oxygen  in  gas  mixtures  containing  carbon 
monoxide  can,  according  to  Kostin,  be  removed  by 
the  use  of  a  pipette  filled  with  iron  wire  gauze  that 
stands  in  a  saturated  solution  of  ferrous  sulphate  to 
which  has  been  added  one-third  of  its  volume  of 


CHAP,  iv  DETERMINATION  OF  OZONE  161 

strong  ammonia.  The  author  has  found  that  it  is 
still  better  to  employ  a  solution  of  ferrous  chloride 
to  which  has  been  added  ammonia  and  sufficient 
ammonium  chloride  to  prevent  the  separation  of 
ferrous  hydroxide. 

OZONE 

A  large  number  of  reagents  may  be  used  for  the 
detection  of  ozone.  For  the  detection  of  such  small 
amounts  of  ozone  as  are  present  in  the  atmosphere, 
so-called  ozone  papers  are  employed. 

Houzeau  has  suggested  that  this  be  prepared  by 
dipping  strips  of  Swedish  filter  paper  into  a  wine-red 
litmus  solution  which  contains  in  a  cubic  centimeter 
about  0.013  g.  of  the  extracted  constituents  dried 
at  100°;  the  paper  is  dried  and  then  impregnated 
to  a  fourth  of  its  length  with  a  one  per  cent  solution 
of  neutral  and  pure  potassium  iodide  free  from  iodate. 
The  dried  paper  must  be  protected  from  the  air,  and 
is  on  this  account  kept  in  tightly  closed  bottles. 

This  paper  is  coloured  slightly  blue  by  from 
0.0002  to  0.0003  nag.  of  ozone.  In  air  containing 
^WoTo  °^  ^8  weight  of  ozone,  the  paper  turns  blue 
at  once.  The  part  of  the  paper  which  is  coloured 
with  the  litmus  solution  and  is  not  impregnated 
with  the  potassium  iodide,  serves  to  show  the  presence 
in  the  air  of  acid  or  alkaline  substances  which  might 
influence  the  reaction.  By  the  action  of  ozone 
the  potassium  iodide  is  decomposed  and  potassium 
hydroxide  is  formed,  which  turns  the  litmus  paper 
blue.  Chlorine,  nitric  acid,  and  other  acid  substances 
do  not  of  course  turn  the  paper  blue  :  in  this  respect 
it  is  superior  to  those  which  follow. 


162  GAS  ANALYSIS  PART  n 

According  to  Schonbein,  strips  of  paper  are 
saturated  with  a  dilute  starch  and  potassium  iodide 
solution  (1  KI  +  10  starch  +  200  water),  and  these 
strips  are  exposed  to  the  air.  A  distinction  of  ten 
shades  from  white  to  dark  blue  is  made. 

Wurster1  uses  tetra-methyl-para-phenylene-dia- 
mene,  which,  upon  taking  up  one  atom  of  oxygen, 
is  quantitatively  oxidised  to  a  blue  colouring  matter, 
and  by  further  union  with  six  oxygen  atoms  changes 
to  a  colourless  substance.  At  Wurster's  suggestion, 
Dr.  Schuchardt  in  Gorlitz  has  made  a  colour  scale 
containing  eight  numbers.  These  are  obtained  b}^  the 
action  of  one  or  two  drops  of  standard  iodine  solutions 
upon  the  tetra-paper  :  — 

The   normal   iodine     ^  3^  y^  irsW  ssW  nr&nr  yy&nr  nreWff 
solutions       corre- 
spond to  the  num- 
bers on  the  colour 
scale I.    II.  HI.     IV.    V.    VI.    VII.  VIII. 

And  hence  contain 
milligrams  of  ac- 
tive oxygen  in  the 
liter 32  16  8  3.2  1.6  0.8  0.24  0.08 

Or  if  16,000  drops  are  reckoned  to  the  liter  :  — 

f    I.      II.      III.      IV.       V.          VI. 

Milligrams       active  j  °-002  °-001  0.0005U0002  0.00001  0.000005 
oxygen  in  a  drop  1  yil.          VIII. 

[  0.0000015  0.0000005 

A  blue  coloration  of  any  one  of  the  three  papers 
may  be  caused  either  by  ozone  or  by  hydrogen 
peroxide. 

1  Berichte  der  deutschen  chemischen  Gesellschaft,  1888,  p.  921. 


CHAP,  iv  DETERMINATION  OF   OZONE  163 

According  to  G.  Erlwein  and  Th.  Weyl1  ozone  im- 
parts to  a  hydrochloric  acid  solution  of  m-pheny- 
lendiamin  a  Burgundy-red  colour,  while  both  hydro- 
gen peroxide  and  nitrous  acid  are 'without  action. 

Engler  and  Wild2  state  that  ozone  may  be  detected 
with  manganous  chloride  paper  which  is  moistened 
with  guaiacum  tincture.  If  ozone  is  present,  a  blue 
colour  appears,  but  the  paper  is  not  affected  by  either 
hydrogen  peroxide  or  nitrous  acid.  Ammonium  car- 
bonate imparts  a  brown  colour  to  the  manganous 
chloride  paper,  but  not  a  blue.  Free  halogens  and 
hypochlorites  must,  however,  be  excluded. 

On  account  of  the  greater  delicacy  of  potassium 
iodide  starch  paper  it  is  better  to  detect  ozone  in  the 
presence  of  hydrogen  peroxide  by  first  removing  the 
latter  by  passing  the  gases  through  a  tube  filled  with 
glass  beads  and  solid  chromic  acid  and  then  intro- 
ducing into  the  gas  a  piece  of  potassium  iodide  starch 
paper.  Hydrogen  peroxide  is  completely  removed 
by  both  dilute  and  concentrated  solutions  of  chromic 
acid,  but  ozone  is  not  acted  upon  by  this  reagent. 
Attention  is  also  called  to  the  fact  that  the  reactions 
of  hydrogen  peroxide  upon  chromic  acid  and  ether, 
and  upon  titanic  acid,  are  not  very  delicate. 

A  very  delicate  reagent  for  hydrogen  peroxide  is 
a  solution  containing  potassium  ferricyanide  and  fer- 
ric chloride.  The  mixture  has  at  first  a  brownish  or 
greenish  colour,  but  small  amounts  of  hydrogen 
peroxide  change  it  to  blue. 

To  detect  ozone,  the  paper  prepared  by  one  of  the 
foregoing  methods  is  fastened  over  the  end  of  a  glass 

1  Berichte  der  deutschen  chemischen  Gesellschaft,  1898,  p.  3158. 
*Ibid.,  1896,  p.  1940. 


164  GAS  ANALYSIS  PART  n 

tube  by  means  of  a  rubber  band,  and  a  measured 
quantity  of  gas  is  drawn  through  the  tube  by  an 
aspirator. 

To  determine  larger  amounts  of  ozone  it  is  best  to 
lead  the  gas  through  a  solution  of  potassium  iodide 
and  to  then  acidify  the  solution  and  titrate  the  iodine 
set  free  with  a  solution  of  sodium  thiosulphate.1 

The  reaction  is  the  following  :  — 

O3  +  2  KI  +  H20  =  02  +  2  KOH  +  I2. 

As  absorbent  either  cinnamon  oil  or  turpentine  oil 

may  be  employed ;  these  take  up  the  ozone  completely, 

and  are  able  to  absorb  very  large  amounts  of  the  gas. 

Especial  attention  should  be  called  to  the  fact  that 

rubber  is  very  strongly  attacked  by  ozone.     When 

,  the    gas    is   to   be 

led  some  distance, 
the  bell  connec- 
tion (Fig.  73)  de- 
vised by  Engler 
and  Nasse  is  well 
adapted  for  mak- 
ing the  connec- 
tions, a  is  a  bent  glass  tube  over  whose  end  a  wide 
glass  tube  is  fitted  by  means  of  a  cork  c.  The  little 
cup  thus  formed  is  filled  with  mercury,  into  which 
dips  the  bell  b. 

NITROGEN 

Specific  gravity,  0.97010.  Weight  of  1  liter,  1.2505. 
Nitrogen  is  but  slightly  soluble  in  water,  one  volume 

1  The  investigations  of  Ladenburg  and  Quasig,  Berichte  der 
deutschen  chemischen  Gesellschaft,  1891,  p.  1184,  have  shown  that 
if  the  solution  is  not  acidified,  erroneous  results  are  obtained. 


CHAP,  iv          DETERMINATION  OF  NITROGEN  165 

of  water  absorbing,  according  to  Bunsen,  at  760  mm. 
pressure  and  £°, 

0.020346  -  0.00053887 1  +  0.000011156 1*  vol.  of  nitrogen: 

hence  at 

5°,  0.01794  vol. 

10°,  0.01607    « 

15°,  0.01478    « 

»20°,  0.01403    " 

Otto  Pettersson  and  K.  Sonden1  state  that  at  a 
pressure  of  760  mm.  1  liter  of  water  absorbs  from 

the  air:  — 

At        0°,  19.53  vol. 

"  6°,  16.34  " 
«  9.18°,  15.58  « 
«  14.10°,  14.16  « 

According  to  Carius,  one  volume  alcohol  takes  up 
at  £°, 

0.126338  -  0.000418 1  +  0.000006 12  vol.  of  nitrogen; 

hence  at 

20°,  0.122378  vol. 

Critical  temperature,  —146°;  critical  pressure,  35 
atmospheres ;  boiling-point,  — 194.4° ;  specific  gravity 
of  liquid  nitrogen,  at  —194. 4°  =  0.885;  melting-point, 
-214°. 

The  residue  in  gas  mixtures  which  cannot  be 
determined  either  by  the  ordinary  absorption  methods 
or  by  combustion  was  earlier  considered  to  be  nitro- 
gen alone.  Consequently  all  of  the  errors  in  the 

1  Eerichte  $er  deutschen  chemischen  Gesellschaft,  1889,  p.  1443, 


166  GAS  ANALYSIS  PART  n 

preceding  determinations  were  concentrated  upon 
the  value  found  for  nitrogen,  and  the  results  for 
this  element  were  the  more  inexact  as  the  gas  mix- 
ture increased  in  complexity.  The  investigations 
of  W.  Ramsay  and  Lord  Rayleigh  have  shown  that 
with  this  nitrogen  the  gases  of  the  argon  group  may 
be  present.  In  order  to  separate  nitrogen  from  these 
gases,  we  may  employ  as  absorption  agent  glowing 
magnesium,  lithium,  or  barium  carbide,  or,  following 
the  procedure  of  Cavendish,  the  nitrogen  may  be 
caused  to  unite  witli  oxygen  by  means  of  a  strong 
electric  spark.  Erdmann  states  that  the  combustion 
is  appreciably  aided  by  the  presence  of  water  vapour 
and  ammonia. 

Maquenne  has  recommended  for  the  absorption 
a  mixture  of  magnesium  with  lime  that  has  been 
strongly  ignited  in  hydrogen. 

In  order  to  be  able  to  judge  of  the  efficiency  of 
these  various  absorption  agents,  the  author  placed  the 
different  substances  in  hard-glass  tubes,  exhausted 
these  tubes  of  air,  and  then  introduced  an  excess  of 
nitrogen.  The  tubes  were  then  heated  to  bright 
redness,  the  nitrogen  was  pumped  out  and  measured, 
and  the  amount  of  that  gas  which  has  been  held  back 
by  each  absorbeht  was  thus  determined. 

The  results  were  as  follows :  — 


DETERMINATION   OF   NITROGEN 


167 


Absorption  Agent  Employed 

^11  a. 
JfJplJl 

mm 

Number  of 
Cubic  Centi- 
meters of  Ni- 
trogen which 
was  absorbed 
in  One  Hour 

1    gram    magnesium    powder, 
medium  fine                   .     • 

14  5 

1  cjram  lithium 

70  5 

1  gram  magnesium  and  5  grams 
quicklime.      The    lime    was 
not  freshly  ignited  .... 
1  gram  magnesium  and  3  grams 
quicklime.      The    lime    was 
not  freshly  ignited.     .     .     . 
1  gram  magnesium  and  8  grams 
quicklime.      The    lime    was 
not  freshly  ignited.     .     .     . 
1  gram  magnesium  and  5  grams 
quicklime.      The    lime    was 
highly  ignited  shortly  before 
the  experiment    

94.5 
86  4 

112.0 
50.0 
31.4 

122  5 

1   gram   magnesium,  5   grams 
freshly  ignited  lime,  and  0.1 
gram  metallic  sodium  .     .     . 
1   gram   magnesium,  5   grams 
freshly  ignited  lime,  and  0.25 
grams  metallic  sodium     .     . 
1   gram  magnesium,  5   grams 
freshly  ignited  lime,  and  0.11 
grams  metallic  mithium   . 

201.0 
196.0 
169.0 

287.0 
326.2 
228.0 

Ignited  lime  with  metallic  sodium  alone  absorbed 
no  nitrogen  whatever,  and  only  very  slight  absorp- 
tion is  effected  by  barium  carbide  alone,  barium  car- 
bide and  potassium,  barium  fluoride  and  sodium,  or 
amorphous  boron  and  silicon.  It  is  possible  that  the 


168 


GAS  ANALYSIS 


PART    II 


barium  carbide  used  in  these  experiments  decomposed 
partially  when  it  was  pulverised. 

From  these  experiments  the  author  considers  that 
the  best  absorption  agent  for  nitrogen  is  a  mixture 
of  one  part  by  weight  of  finely  powdered  magnesium 
with  five  parts  by  weight  of  freshly  ignited  lime  in 
pieces  about  as  large  as  poppy  seeds  and  0.25  part 
by  weight  of  metallic  sodium.  The  magnesium 
should  be  intimately  mixed  with  the  ignited  lime, 
but  it  is  sufficient  to  add  the  sodium  in  the  form  of 
a  number  of  pieces  each  about  half  as  large  as  a  pea. 
The  layer  of  oxide  covering  the  metallic  sodium 
should  be  first  removed,  and  the  metal  should  be 
added  to  the  mixture  just  before  using. 

The  "  analytical  absorbing  power  "  of  the  mixture, 
based  upon  the  amount  of  the  magnesium,  is  8.15  ccm. 


GASES  OF  THE  ARGON  GROUP 


d 

°o 

Is  ' 

-I 

•a  2 

Pi 

* 

jj 

Ml 

f1  a 

§  g 

s  s 

^        ^£ 

VH    ^ 

r£-      -*-* 

1 

8 

1 

.si 

^  ta 

II 

*-g    m 

5  ^ 

^  qH  c 

*o    >• 

&8 

02  O 

?S 

1 

H 

•»  «5 

mm. 

M" 

Helium  . 

1.98 

0.14 

0.18 

Neon.    . 

9.96 

Argon     . 

19.96 

—187.9 

-186.1 

-117.4° 

40.2 

1.212 

1.352 

1.788 

Krypton, 

40.78 

—169. 

—151.67 

-  62.5° 

41.24 

2.155 

Xenon    . 

64. 

—140. 

-109.1 

+  14.75° 

43.5 

3.52 

Since  the  gases  are  monatomic,  their  atomic 
weights  are  twice  their  specific  gravities  as  re- 
ferred to  hydrogen. 


CHAP,  iv  GASES  OF  THE   AKGON   GROUP  1C9 

Helium  cannot  be  condensed  even  at  a  tempera- 
ture of  -  264°.  100  com.  of  water  at  18°  absorbs  0.7 
ccm.  of  the  gas. 

One  liter  of  water  at  room  temperature  dissolves 
40  ccm.  of  gas. 

Neon  and  helium  may  be  separated  by  means  of 
the  different  solubilities  and  liquid  oxygen. 

After  the  absorption  of  nitrogen  the  gases  of  the 
argon  group  remain  behind.  Their  separation  may 
be  effected  by  cooling  the  gases  down  to  extremely 
low  temperatures  by  means  of  liquid  air,  and  then 
allowing  them  to  fractionally  distil.  The  purity  of 
the  gases  may  be  judged  from  the  specific  gravity. 

The  gases  may  be  recognized  from  their  spectra, 
which  may  be  obtained  by  bringing  the  gases  into 
Pliicker  tubes,  and  using  an  induction  coil  of  from  4 
to  7  mm.  spark  length,  and  furnishing  about  20  sparks 
per  second. 

Argon  and  xenon  exhibit  very  noticeable  changes 
in  the  positions  of  the  spectrum  line  when  a  Leyden 
jar  is  introduced  into  the  circuit,  but  this  does  not 
cause  a  change  in  the  spectra  of  the  other  gases  of 
the  argon  group. 

Helium  is  chiefly  characterised  by  a  very  bright 
yellow  line,  which  is  very  close  to  the  sodium  lines, 
but  lies  slightly  nearer  the  violet  end  of  the  spectrum 
than  do  the  latter. 

Neon  shows  red,  orange,  and  yellow  lines,  while 
krypton  yields  a  brilliant  green  line. 

The  argon  spectrum  varies  greatly  with  the  press- 
ure and  the  strength  of  the  discharge,  and  shows  a 
large  number  of  lines  in  the  red,  green,  and  violet 
parts  of  the  spectrum.  The  spectrum  lines  of  neon, 


170  GAS  ANALYSIS  PART  n 

krypton  and  xenon  cannot  be  seen  in  the  spectrum 
of  impure  argon.  Even  photographs  of  the  spectra 
fail  to  disclose  them. 

Xenon  shows  a  very  brilliant  line  in  the  blue. 

Further  details  may  be  found  in  the  published 
articles  of  Rayleigh,  Ramsay,  and  Crookes,  and  col- 
oured charts  of  the  spectra  are  given  in  the  second 
edition  of  Erdmann's  Lehrbuch  der  anorganischen 
Ohemie. 

Tubes  rilled  with  argon  may  be  easily  prepared 
by  extracting  the  gas  from  atmospheric  air.  Helium 
can  be  obtained  by  heating  pulverised  cleveite  with 
twice  its  weight  of  primary  potassium  sulphate,  using 
the  apparatus  shown  in  Fig.  12. 

For  the  separation  of  the  gases  of  the  argon  group 
the  author  would  recommend  the  apparatus  shown  in 
Fig.  74.  B  is  a  tube  of  hard  glass  which  is  filled 
with  a  mixture  of  one  part  by  weight  of  metallic 
magnesium,  0.2  parts  of  metallic  sodium,  and  five 
parts  by  weight  of  freshly  ignited  lime  that  has 
been  broken  into  pieces  about  as  large  as  poppy 
seeds.  The  tube  A  permits  of  the  easy  introduction 
of  the  gases  to  be  examined.  The  spaces  D,  JZ,  and 
F  are  filled  with  coarse-grained  copper  oxide,  potas- 
sium hydroxide,  and  phosphorus  pentoxide  respec- 
tively, and  to  these  is  attached  an  air-pump,  not 
shown  in  the  figure,  by  means  of  which  the  gases 
can  be  removed  and  collected.  (The  Topler  air- 
pump,  described  on  p.  393,  may  be  used  for  this 
purpose.)  The  tubes  are  connected  by  means  of 
U-shaped  thin  glass  tubes,  which  are  joined  by  pieces 
of  rubber  tubing.  These  joints  are  made  completely 
air-tight  by  immersing  them  in  mercury  which  is 


172  GAS  ANALYSIS  PART  n 

placed  in  small  beakers.  This  arrangement  makes 
it  easy  to  connect  and  take  apart  the  different  parts 
of  the  apparatus,  and  gives  it  sufficient  freedom  of 
motion  to  render  it  but  slightly  liable  to  breakage. 
By  means  of  the  two-way  stopcock  c  the  tubes  A  and 
B  may  be  brought  into  communication  with  each 
other,  or  either  one  of  them  may  be  joined  to  the 
air-pump.  This  stopcock  should  be  very  carefully 
ground.  Lanoline  has  been  found  to  be  a  satisfac- 
tory lubricant  for  the  stopcocks. 

The  stopcocks  6  and  d  are  also  provided  with  mer- 
cury cups  to  insure  the  tightness  of  the  joint. 

The  bulb  a  is  filled  with  phosphorus  pentoxide. 
Loose  wads  of  asbestos  are  placed  in  all  of  the  tubes 
which  contain  absorbing  agents  so  as  to  prevent  par- 
ticles of  these  substances  from  being  carried  along 
through  the  tubes. 

In  making  an  analysis,  all  the  tubes  are  first  nearly 
exhausted  of  air  with  an  air-pump,  and  mercury  is 
drawn  up  in  the  tube  A  until  it  reaches  the  stop- 
cock 5.  The  tube  B  is  then  slightly  heated  by  means 
of  a  row  of  Bunsen  burners.  This  causes  an  evolu- 
tion of  a  considerable  amount  of  gas  from  the  mix- 
ture contained  in  the  tube.  When  the  tube  is  again 
nearly  free  from  air,  the  tube  D  is  then  heated  and 
the  exhaustion  is  continued  with  the  air-pump  until 
the  amount  of  gas  removed  with  each  stroke  of  the 
pump  is  so  small  as  to  be  negligible.  This  operation 
takes  about  two  hours.  If  the  pressure  in  the  appa- 
ratus is  to  be  reduced  to  a  very  low  point,  it  is  abso- 
lutely necessary  that  the  air-pump  should  be  perfectly 
dry  on  the  inside  and  that  the  mercury  should  be  free 
from  particles  of  dust.  Like  many  other  liquids, 


CHAP,  iv          GASES  OF  THE  ARGON   GROUP  173 

mercury  possesses  the  property  of  holding  dust  in 
suspension,  and  this  dust  will  not  completely  sepa- 
rate even  after  days  of  standing.  If  the  mercury 
air-pump  and  the  mercury  are  not  thoroughly  clean, 
the  pumping  may  be  continued  for  hours  without 
producing  high  dilution  of  the  gas  in  the  apparatus, 
but  the  exhaustion  is  accomplished  in  a  very  short 
time  if  the  apparatus  is  clean  and  perfectly  dry. 

When  the  apparatus  has  thus  been  made  ready, 
the  gas  to  be  examined  is  introduced  into  A  from 
the  gas  pipette  6r.  It  is  necessary  to  previously  free 
this  gas  mixture  from  all  absorbable  and  combustible 
constituents.  The  stopcock  c  is  closed,  and  the  gas 
is  allowed  to  enter  the  bulb  a  by  slowly  opening  the 
stopcock  b.  a  is  filled  with  phosphorus  pentoxide, 
b  is  then  closed,  and  c  is  turned  into  such  position 
that  the  tube  B  communicates  with  the  bulb  a.  Upon 
carefully  opening  b  mercury  rises  in  A  and  drives 
before  it  any  gas  therein  contained,  but  the  greatest 
care  must  be  exercised  to  prevent  any  mercury  what- 
ever from  entering  the  bulb  a.  If  only  a  very  small 
volume  of  gas  is  at  one's  disposal,  it  can  be  swept  up 
into  the  apparatus  by  means  of  pure  hydrogen  gas, 
which  is  introduced  into  A  from  a  gas  pipette.  After 
about  a  quarter  of  an  hour  the  stopcock  d  is  closed 
and  the  residual  gases  of  the  argon  group  may  be 
allowed  to  enter  D,  E,  and  F.  Gas  is  then  again 
drawn  out  from  a.  The  stopcock  d  is  necessary  to 
prevent  the  too  rapid  flow  of  the  gases  through  D, 
E,  and  F,  and  the  consequent  passage  of  unburned 
gases  through  the  glowing  copper  oxide  in  D.  If 
the  stopcock  d  were  not  present,  the  gas  mixture 
would  of  course  rush  with  great  rapidity  through  D, 


174  GAS  ANALYSIS  PART  n 

E,  and  F  into  the  exhausted  bulb  of  the  mercury 
air-pump.  The  necessity  for  introducing  glowing 
copper  oxide,  caustic  potash,  and  phosphorus  pentox- 
ide  into  the  apparatus  arises  from  the  fact  that  it 
is  impossible  to  completely  remove  the  last  traces  of 
absorbable  gases  by  means  of  the  ordinary  absorption 
methods. 

When  the  whole  gas  volume  under  examination 
has  been  in  the  tubes  B,  D,  E,  and  F  for  some  time, 
the  stopcock  d  is  carefully  opened  and  the  gas  resi- 
due in  the  apparatus  is  drawn  over  with  the  mercury 
air-pump  into  the  graduated  tube  E  (see  Fig.  115) 
and  is  here  measured.  If  the  gas  volume  is  very 
small,  it  is  better  to  transfer  it  directly  to  a  measur- 
ing bulb  and  to  measure  it  in  the  apparatus  for  exact 
gas  analysis. 

If  a  spectroscopic  examination  of  the  gas  residue 
is  desired,  there  is  introduced  between  the  stopcock 
d  and  the  mercury  air-pump  a  four-way  glass  tube. 
To  one  arm  of  this  tube  is  attached  a  glass  tube  filled 
with  gold  leaf  and  to  this  is  joined  a  Pliicker  tube. 
To  the  other  three  arms  of  the  four-way  piece  are 
attached  the  stopcock  d,  the  mercury  air-pump,  and 
a  manometer  tube.  The  manometer  tube  is  indis- 
pensable, because  the  spectra  of  the  gases  vary  with 
the  pressure.  If  this  spectroscopic  examination  is 
to  be  made,  it  is  best  to  first  measure  the  gases  and 
then  to  transfer  them  to  A  by  means  of  a  pipette  and 
to  allow  them  to  again  pass  through  the  tube  B.  The 
tubes  B  and  D  always  break  upon  cooling,  so  that  it 
is  necessary  to  keep  them  hot  during  the  whole  pro- 
cedure. The  temperature  of  these  two  tubes  should 
be  raised  to  the  softening  point  of  the  glass. 


CHAP,  iv        DETERMINATION  OF   HYDROGEN  176 

HYDROGEN 

Specific  gravity,  0.069234  ;  weight  of  1  liter, 
0.089582;  critical  temperature,  233°;  critical  press- 
ure, 15  atmospheres  ;  boiling-point,  about  —  240°  ; 
specific  gravity  (water  =  1)  of  liquid  hydrogen,  0.07. 

According  to  L.  W.  Winkler,1  one  volume  of  water 

absorbs  at 

0°,  0.02148  vol.  hydrogen 

5°,  0.02044 
10°,  0.01955  « 

15°,  0.01883 
20°,  0.01819 

At  t°  alcohol  takes  up 

0.06925  -  0.0001487*  + 0.000001  f2  vol.  of  hydrogen  ; 

hence  at 

20°,  0.066676  vol.  (Bunsen). 

Hydrogen  can  be  very  easily  determined  by  burn- 
ing it  with  oxygen.  Either  air  is  used,  or,  as  proposed 
by  Bunsen,  pure  oxygen  made 
in  retorts  blown  from  a  glass 
tube,  and  of  from  6  to  10  ccm. 
capacity  (Fig.  .75).  These  re- 
torts are  half  filled  with  dried 
and  pulverised  potassium  chlo- 
rate, and  the  end  of  the  delivery  Fio  75 
tube  is  then  heated  at  a  and  bent 
upward.  The  air  is  first  driven  out  by  a -rapid  evo- 
lution of  oxygen,  and  the  gas  is  then  led  directly 
into  the  eudiometer,  care  being  taken  that  the  volume 

1  Berichte  der  deutschen  chemischen  Gesellschaft,  24,  89.  See 
also  Timofejew,  Zeitschr.  fur  phys.  Chem.  6,  141. 


176  GAS  ANALYSIS  PART  n 

of  oxygen  does  not  amount  to  more  than  three  or 
four  times  that  of  the  hydrogen  to  be  determined. 

The  quantity  of  hydrogen  present  is  J  of  the 
volume  disappearing  in  the  combustion.  If  the 
mixture  contains  absorbable  constituents  also,  these 
are  first  absorbed  and  the  residual  gas  is  then  used 
for  the  analysis. 

When  nitrogen  is  present  a  considerable  error  may 
be  caused  by  not  avoiding,  in  the  combustion,  the 
temperature  at  which  nitric  acid  is  formed.  Hence 
one  should  never  neglect  to  calculate,  after  the 
experiment,  the  proportion  of  nitrogen  to  the  oxy- 
hydrogen  gas  burned.  If  this  was  less  than  6  to  1, 
the  analysis  must  be  repeated  with  the  addition  of  so 
much  air  that  this  proportion  or  a  still  greater  amount 
of  nitrogen  will  be  present. 

If,  on  the  other  hand,  the  proportion  of  hydrogen 
to  incombustible  gas  be  very  small,  such  an  amount 
of  electrolytic  oxyhydrogen  gas  is  added  that  com- 
plete combustion  will  result.  The  oxyhydrogen  gas 
disappears  completely  in  the  combustion,  and  hence 
need  not  be  exactly  measured. 

An  accurately  measured  amount  of  pure  hydrogen 
mixed  with  an  excess  of  air  may  be  used  instead  of 
the  oxyhydrogen  gas.  The  contraction  resulting 
from  the  hydrogen  added  must  then  be  allowed 
for. 

The  combustion  is  made  either  in  the  explosion 
pipette  by  ignition  with  an  electric  spark,  or  in  a 
glass  tube  filled  with  palladium-black,  or,  as  Winkler 
has  proposed,  with  palladium  asbestos.  The  advan- 
tage of  the  combustion  with  palladium  is,  that  in  a 
mixture  of  hydrogen,  marsh-gas,  and  nitrogen,  the 


CHAP,  iv        DETERMINATION   OF  HYDROGEN 


177 


hydrogen  alone  may  be  burned  :    this  is  known  as 
fractional  combustion. 

Hydrogen  may  also  be  very  accurately  determined 
by  means  of  the  method  proposed  by  Dennis  and 
Hopkins l  with  the  combustion  pipette  described  on 
p.  138  and  the  arrangement  of  apparatus  shown  on 
p.  294.  In  this  method  the  hydrogen  is  first  intro- 
duced into  the  combustion  pipette  and  a  mixture  of 
equal  parts  of  oxygen  and  air  more  than  sufficient 
for  its  combustion  is  measured  off  into  the  burette. 
The  burette  and  pipette  are  then  connected,  the 
spiral  is  heated  to  redness  by  means  of  an  electric 
current,  and  the  mixture  of  air  and  oxygen  is  slowly 
passed  over  from  the  burette  into  the  pipette.  The 
combustion  of  the  hydrogen  is  complete  almost  as 
soon  as  sufficient  oxygen  has  been  introduced.  When 
the  combustion  is  finished,  the  residual  gas  is  passed 
back  into  the  burette  and  measured.  The  results 
of  a  series  of  determinations  of  hydrogen  made  with 
this  method  are  given  in  the  following  table  :  — 


Hydrogen  taken  99.6 
Oxygen  and  air 

added 99.6 

Total  .  .  .  199.2 
Residue  after 

combustion  .  .  50.0 
Contraction.  .  .  149.2 
Equivalent  to 

hydrogen  .  . 


II.  III. 

ccm.  ccm. 

100.0  98.6 

99.95  99.9 

199.95  198.5 

50.1  50.8 

149.85  147.7 


Per  ct 

Hydrogen  found  99.9 


99.47    99.9      98.47 
Per  ct.  Per  ct. 

99.9    99.9 


IV.         V.  VI.       VII.      VIII. 

ccm.      ccm.  ccm.      ccm.       ccm. 

99.8      99.4  95.35    97.5      51.15 

100.0      99.1  96.6      99.75    48.95 

199.8    198.5  191.95  197.25  100.10 

50.55    49.7  49.1      51.2      23.4 

149.25  148.8  142.85  146.05    76.7 

99.5      99.3  95.23    97.37    51.13 

Per  ct.  Per  ct.  Per  ct.  Per  ct.  Per  ct. 

99.7    99.9  99.9    99.9    100.0 


1  J.  Am.  Chem,  Soc.,  21, 


178  GAS  ANALYSIS  PART  n 

FRACTIONAL  COMBUSTION 

The  possibility  of  separating  gases  from  one  an- 
other by  fractional  combustion  was  first  observed  by 
W.  Henry,  and  used  by  him  for  the  analysis  of  gas 
mixtures. 

Henry  states l  that  carbon  monoxide  and  hydrogen 
can  be  removed  by  combustion  from  a  mixture  of 
hydrogen,  carbon  monoxide,  marsh-gas,  and  nitrogen 
by  leading  these  gases  over  platinum  sponge  heated 
to  177°. 

Since  no  convenient  method  for  carrying  out  this 
reaction  was  devised,  it  had  not  been  adopted  into 
gas  analysis. 

While  studying  the  occlusion  of  hydrogen  by 
palladium,  the  author  succeeded  in  working  out  a 
method2  by  which  the  hydrogen  in  a  mixture  with 
marsh-gas  and  nitrogen  may  be  fractionally  burned 
in  a  very  short  time  at  the  temperature  of  the  room. 

The  following  points  concerning  the  fractional 
combustion  were  determined:  — 

1.  A  mixture  of  hydrogen  with  oxygen  in  excess, 
led  over  palladium  sponge  which  has  been  superfi- 
cially oxidised  by  heating  it  to  redness  and  allowing 
it  to  slowly  cool,  is  completely  burned.     The  reaction 
begins  at  the  temperature  of  the  room,  and  so  much 
heat  is  developed  that  the  palladium  begins  to  glow 
and  the  gases  explode  if   they  are  present  in  the 
proper  proportions  to  form  oxyhydrogen  gas. 

2.  Marsh-gas,  mixed  with  oxygen,  and  led  over 
palladium,  does  not  burn  at  temperatures  up  to  100°  ; 

1  Annals  of  Philosophy,  25,  428. 

2  Serichte  der  deutschen  chemischen  Gesellschaft,  1879,  p.  1006. 


CHAP,  iv        DETERMINATION   OF   HYDROGEN  179 

the  combustion  begins  at  about  200°.  A  mixture  of 
29.3  ccm.  marsh-gas  and  70.6  ccm.  oxygen,  led  several 
times  over  palladium  heated  to  from  200°  to  220°, 
underwent  a  contraction  of  3  ccm. 

3.  Mixtures  of  hydrogen,  marsh-gas,  and  oxygen, 
in  the  proportions  necessary  for  combustion,  often 
explode  very  violently  when  brought  into  contact 
with  palladium ;  the  author  did  not  succeed  in  pre- 
venting the  explosion  with  certainty,  even  by  the 
interposition  of  cooling  metals  and  by  the  use  of  thin 
tubes  standing  in  water. 

4.  If  mixtures  of  hydrogen,  marsh-gas,  and  air, 
oxygen  being  present  in  excess,  be  led  over  palladium 
at  ordinary  temperatures  up  to  100°,  the  hydrogen 
alone  burns,  and  the  marsh-gas  is  not  at  all  acted 
upon,  provided  that  the  palladium  is  not  allowed  to 
heat  up  too  much  during  the  reaction.     No  explosion 
takes  place  here. 

If  the  water  formed  in  the  combustion  is  driven  off 
from  time  to  time  by  heating  the  palladium  upon  the 
cover  of  a  platinum  crucible,  the  palladium  does  not 
then  need  to  be  regenerated  after  each  experiment, 
but  may  be  used  as  it  is  for  a  large  number  of  com- 
bustions. Since  the  palladium  plays  only  an  inter- 
mediary role,  a  very  E  E 
small  amount  of  it  suf- 
fices. 

In  the   following  re- 
searches  0.5   g.   of  the  ^^J 
metal  was   placed   in  a 
U-shaped      glass      tube 

(Fig.  76),  which  by  means  of  two  capillary  tubes  E 
was  connected  on  the  one  side  with  a  gas  burette, 


,80 


GAS   ANALYSIS 


PART  II 


and  on  the  other  with  a  gas  pipette  filled  with  water. 
The  U-shaped  tube  was  kept  cool  by  immersing  it  in 
a  beaker  glass  containing  water  of  the  temperature 
of  the  room.  The  gases  were  led  through  so  slowly 
that  the  metal  either  did  not  glow  at  all  or  was 
heated  to  redness  at  some  points  for  only  a  very 
short  time.  A  single  passage  of  the  gas  mixture 
through  the  palladium  sufficed  usually  for  complete 
combustion. 


Composition  of  the  Gas  Mixture 

Hydrogen 

Resulting 

calculated 

Contraction 

from  the 

Hydrogen 

Marsh-gas 

Air 

Contraction 

1.5 

12.0 

85.1 

2.3 

1.5 

-  3.0 

8.3 

86.5 

4.5 

3.0 

5.1 

12.3 

86.0 

7.6 

5.0 

9.3 

7.1 

83.7 

14.1 

9.4 

13.7 

7.3 

77.5 

20.3 

13.5 

14.1 

5.4 

81.2 

21.2 

14.1 

14.6 

4.5 

80.6 

22.1 

14.7 

13.1 

6.0 

80.3 

19.7 

13.1 

In  the  last  experiment  the  palladium  tube  stood  in 
water  at  100°. 

From  these  experiments  it  follows  that,  with  the 
addition  of  air,  the  hydrogen  in  any  mixture  of 
hydrogen,  marsh-gas,  and  nitrogen  may  be  determined 
by  fractional  combustion  at  about  100°.  For  mix- 
tures which,  like  all  furnace  or  generator  gases,  con- 
tain large  amounts  of  nitrogen,  pure  oxygen  also  may 
be  employed. 


CHAP,  iv         DETERMINATION  OF   HYDROGEN  181 

Cl.  Winkler  has  later  suggested  that,  in  place  of 
the  tube  filled  with  palladium-black,  there  be  used  a 
capillary  tube  which  contains  a  very  small  quantity  of 
palladium  asbestos,  and  which  is  heated  from  without 
by  a  little  flame  to  the  temperature  of  the  reaction. 
If  hydrogen  alone  is  to  be  burned,  this  arrangement 
is  quite  suitable  ;  if,  however,  a  fractional  combustion 
is  to  be  made,  the  author  prefers  the  arrangement 
described  above,  since  with  direct  heating  it  is  diffi- 
cult to  control  the  temperature.  If  the  temperature 
rises  beyond  200°,  a  part  of  the  marsh-gas  is  burned 
with  the  hydrogen.  If,  however,  the  palladium  tube 
stands  in  hot  water,  the  temperature  easily  regulates 
itself. 

Hydrogen  may  also  be  determined  by  absorption 
with  palladium,  potassium,  or  sodium. 

•.. 
ABSORPTION  OF  HYDROGEN  BY  PALLADIUM 

Many  endeavours  to  find  an  absorption  method  for 
separating  hydrogen  from  other  gases  led  the  author 
to  ascertain  the  conditions  under  which  the  property 
of  palladium  of  condensing  large  amounts  of  hydrogen 
at  100°,  known  as  occlusion,  may  be  used  for  quan- 
titatively separating  hydrogen  from  marsh-gas  and 
nitrogen,  as  well  as  from  some  other  gases. 

Concerning  the  purely  chemical  relations  between 
hydrogen  and  palladium,  a  large  number  of  experi- 
ments have  shown  the  author  — 

1.  That,  on  the  one  hand,  palladium  loses,  as  is 
well  known,  its  silver-white  metallic  colour  when 
heated  nearly  to  a  red  heat  in  the  presence  of  oxygen, 


182  GAS  ANALYSIS  PART  n 

and  becomes  superficially  covered  with  a  thin  layer 
of  palladious  oxide,  and  that  this  palladious  oxide  is, 
on  the  other  hand,  able  to  burn  hydrogen  at  ordinary 
temperatures  with  evolution  of  heat,  so  that  the  inter- 
mixed or  reduced  metallic  palladium  reaches  the  tem- 
perature at  which  it  can  absorb  large  quantities  of 
hydrogen  by  occlusion. 

2.  That  the  hydrogen  taken  up  by  occlusion  may 
be  completely  removed  either  by  heating  the  pal- 
ladium in  a  vacuum  to  100°,  or  by  leading  air  over 
the  metal  at  ordinary  temperatures.     This  latter  was 
proved  by  saturating  palladium  with  hydrogen  to  the 
fullest  extent  possible,  by  placing  the  metal  in  a  red- 
hot  tube  and  leading  dry  hydrogen  over  it,  and  then 
letting  it  slowly  cool  in  the  current  of  hydrogen. 
Air  having  been  led  over  the  palladium  thus  pre- 
pared,  the    metal   was   placed   in    a  porcelain  tube 
connected  with  a  Topler  air-pump,  and  the  tube  was 
raised  to  bright  red  heat,  but  no  further  trace  of 
hydrogen  could  be  obtained. 

3.  That  upon  leading  air  over  palladium  which 
had  occluded  large  quantities  of  hydrogen,  the  tem- 
perature of  the  metal  is  raised  so  high  by  the  com- 
bustion that  palladious  oxide  is  again  formed. 

A  mixture  of  hydrogen,  marsh-gas,  and  nitrogen  is 
indifferent  to  pure  metallic  palladium,  but  a  strong 
reaction  takes  place  when  the  gases  are  brought  into 
contact  with  palladium  sponge  which  has  been  cov- 
ered with  a  very  thin  layer  of  palladious  oxide  by 
heating  it  to  glowing  and  letting  it  cool  not  too 
rapidly.  The  palladium  becomes  warm  and  the 
hydrogen  disappears  completely,  provided  the  gas  is 
brought  into  sufficiently  intimate  contact  with  the 


CHAP,  iv          DETERMINATION  OF   HYDROGEN  183 

palladium.  If  air  be  led  over  the  palladium  after 
the  completion  of  the  reaction,  which  is  clearly  indi- 
cated by  the  cooling  of  the  metal,  the  hydrogen  in 
the  metal  burns  and  the  surface  is  again  covered 
with  palladious  oxide.  The  palladium  thus  regener- 
ated with  air  is  at  once  ready  for  a  new  absorption ; 
with  a  few  (2.5)  grams  of  palladium  sponge  in  a 
glass  tube  an  unlimited  number  of  absorptions  may 
be  made  without  the  aid  of  external  heat.  The 
reaction  concerned  is  partly  combustion,  partly 
occlusion. 

What  has  just  been  said  holds  true  only  when  the 
gases  are  mixed  in  certain  proportions,  since  of  course 
the  conditions  for  the  regeneration  of  the  palladium 
exist  only  when  large  amounts  of  hydrogen  have  been 
occluded.  The  presence  of  sufficient  hydrogen  can 
easily  be  brought  about  by  the  addition  of  pure 
hydrogen  made  in  the  apparatus  already  described. 
(The  procedure  here  is  similar  to  the  addition  of  oxy- 
hydrogen  gas  in  the  explosion  analysis.)  Yet  even 
when  the  hydrogen  is  added,  the  reaction  fails  if  the 
gas  mixture  to  be  analysed  contains  certain  other  sub- 
stances, as  it  always  does  in  technical  analyses.  We 
have  there  to  deal  with  very  complicated  gas  mixtures 
from  which  the  other  gases — carbon  dioxide,  heavy 
hydrocarbons,  oxygen,  carbon  monoxide,  etc.  —  must 
first  be  separated  by  absorption.  The  gases  just  men- 
tioned may  in  a  few  minutes  be  separated  by  absorp- 
tion with  great  ease  and  with  a  completeness  more 
than  sufficient  for  practical  ends,  so  that  less  than 
tenths  of  a  per  cent  of  the  gases  remain  in  the  gas 
residue.  It  is,  however,  very  difficult,  and,  in  a  short 
space  of  time,  impossible  to  separate  traces  less  than 


184  GAS  ANALYSIS  PART  n 

tenths  per  thousand,  for  the  well-known  reason  that 
the  rapidity  of  absorption  diminishes  with  the  dilution 
of  the  gas.  And  since,  further,  some  of  the  absorbents 
give  up  gases — the  solutions  of  cuprous  chloride  give 
off,  according  to  whether  they  are  acid  or  alkaline, 
either  hydrochloric  acid  or  ammonia — the  residue 
which  remains  after  the  absorption  of  the  absorbable 
gases  consists  of  hydrogen,  nitrogen,  and  marsh-gas, 
and  an  undeterminable  amount  of  carbon  dioxide, 
heavy  hydrocarbons,  oxygen,  and  vapours  of  hydro- 
chloric acid  or  ammonia.  This  gas  residue  deports 
itself  differently  from  the  mixture  of  pure  hydrogen, 
nitrogen,  and  marsh-gas  ;  with  quite  active  palladium 
sponge  coated  with  a  very  thin  layer  of  oxide,  no 
heating-up  and  no  absorption  take  place. 

Upon  investigating  the  behaviour  of  different  gases 
in  the  presence  of  hydrogen  toward  palladium  which 
contains  palladious  oxide,  it  was  found  that  hydrogen 
could  be  sharply  separated  by  this  reaction  — 

(1)  from  marsh-gas  and  nitrogen, 

(2)  from  ethylene  and  nitrogen, 

(3)  from  carbon  dioxide  and  nitrogen  ; 

that  aqueous  vapour  and  traces  of  ammonia  do  not 
interfere  ;  but  that  carbon  monoxide,  large  quantities 
of  benzol  vapour  or*  alcohol  vapour,  and  traces  of 
hydrochloric  acid  do  interfere. 

The  reason  for  this  behaviour  is  that  the  affinity  of 
the  gases  last-named  for  the  oxygen  of  the  palladious 
oxide  equals  or  exceeds  that  of  hydrogen,  so  that 
they  first  burn  at  the  expense  of  the  palladious  oxide, 
and  in  so  doing  do  not  develop  enough  heat  to  make 
the  occlusion  of  the  hydrogen  possible. 


CHAP,  iv         DETERMINATION  OF   HYDROGEN  185 

Since  we  have  here  to  deal  with  a  combustion 
which,  as  it  happens,  takes  place  at  ordinary  tempera- 
tures, the  author  believes  it  must  be  possible  to  sepa- 
rate the  gases  in  question  with  the  aid  of  other 
metallic  oxides  and  other  temperatures,  if  we  could 
only  succeed  in  raising  the  temperature  slowly  and 
exactly  with  the  help  of  suitable  thermostats,  and  in 
keeping  the  interior  of  the  tube  at  the  same  tempera- 
ture as  that  prevailing  on  the  outside  by  diluting  the 
metallic  oxides  with  metals.  In  this  way  it  might  be 
possible,  with  the  use  of  simple  apparatus,  to  make  the 
whole  gas  analysis  by  fractional  combustion.  We  may 
call  to  mind  in  this  connection  that  in  badly  performed 
elementary  analyses  tarry  products  distil  over  feebly 
glowing  copper  oxide. 

If  oxygen  is  present  with  hydrogen  in  the  pal- 
ladium reaction,  the  oxygen  is  burned  completely  to 
water.  But  the  combustion  of  the  marsh-gas  may 
also  take  place  if  the  heat  rises  too  much,  i.e.  at  tem- 
peratures near  that  of  red  heat.  This  rise  of  tem- 
perature may  be  caused  by  improperly  preparing  the 
palladium  in  spherical  masses,  so  that  the  heat  evolved 
during  the  reaction  is  then  only  insufficiently  set  free 
by  radiation.  The  difficulties  which  stand  in  the  way 
of  using  palladium,  because  of  the  particulars  just 
mentioned,  are  completely  avoided  if  the  absorbable 
gases  are  first  removed  as  far  as  possible,  if  only  an 
ammoniacal  cuprous  chloride  solution  is  used,  if  for 
the  combustion  of  the  last  traces  of  carbon  monoxide, 
ammonia,  etc.,  somewhat  more  palladium,  4  to  5  gr., 
is  used,  and  if  during  the  reaction  itself  the  tube  with 
the  palladium  stands  in  water  of  from  90°  to  100° 
temperature.  Before  using  the  palladium  it  is  heated, 


186  GAS  ANALYSIS  PART  n 

in  portions  of  about  1  g.  at  a  time,  nearly  to  red- 
ness upon  the  cover  of  a  platinum  crucible,  so  that  it 
is  covered  with  a  larger  quantity  of  palladious  oxide 
than  would  be  formed  by  merely  leading  air  over  it. 
The  warm  water  in  which  the  tube  stands  serves  in 
the  beginning  to  give  the  gases  the  temperature 
necessary  to  start  the  combustion,  and  later  it  pre- 
vents the  temperature  inside  the  palladium  tube 
being  raised  too  high  by  the  reaction. 

Palladium-black  is  still  more  active  than  the  palla- 
dium sponge  which  has  been  coated  with  palladious 
oxide  by  heating  it  to  redness. 

This  palladium-black  is  made  by  reducing  pal- 
ladious chloride  with  alcohol  in  a  strongly  alkaline 
solution,  the  same  method  being  used  in  preparing 
platinum -black  from  platinum  chloride.  Palladium- 
black,  which  is  active  even  in  the  presence  of  vapours 
of  hydrochloric  acid,  is  either  an  oxygen  compound  of 
palladium  or  a  mixture  of  metallic  palladium  with 
palladious  oxide. 

The  arrangement  of  the  apparatus  for  carrying  out 
the  reaction  is  shown  in  Fig.  77.  The  gas  burette 
A  and  the  gas  pipette  B  are  joined  together  by 
means  of  the  capillary  tubes  E  and  the  tube  H.  This 
tube  H  is  of  about  4  mm.  internal  diameter  and 
20  cm.  total  length,  and  it  contains  4  g.  of  palladium 
sponge. 

The  gas  pipette  upon  the  stand  Gr  is  filled  with 
water,  and  its  only  use  is  to  render  it  possible  to 
repeatedly  pass  the  gas  through  the  palladium  tube. 

To  determine  the  amount  of  hydrogen  present  in 
a  mixture  of  hydrogen,  nitrogen,  and  marsh-gas,  from 
which,  so  far  as  possible,  the  absorbable  constituents 


"FIG.  77. 


188  GAS   ANALYSIS  PART  n 

have  already  been  removed,  measure  the  gas  in  the 
burette,  join  it  in  the  manner  described  to  the  pipette 
B,  which  is  filled  with  water  nearly  to  »,  place  the 
tube  H  in  a  large  beaker,  containing  warm  water  of 
from  90°  to  100°,  and,  after  opening  the  pinchcock  d, 
drive  the  gas  three  times  back  and  forth  through  the 
palladium  by  raising  and  lowering  the  tube  a.  Then 
replace  the  hot  water  with  water  of  the  temperature 
of  the  room,  and  lead  the  gas  residue  twice  back  and 
forth  through  the  tube  in  order  to  completely  cool 
the  gas.  It  is  in  this  manner  possible  to  absorb  with 
certainty  every  particle  of  hydrogen.  Upon  drawing 
the  gas  so  far  back  into  the  measuring  tube  that  the 
water  in  the  pipette  again  stands  near  i,  the  differ- 
ence between  the  two  measurements  made  before  and 
after  the  absorption  corresponds  to  the  hydrogen  + 
the  amount  of  oxygen  in  the  air  enclosed  in  the 
U-tube  when  the  apparatus  was  put  together.  This 
air  volume,  and  therefrom  its  oxygen  contents,  may 
be  determined  with  sufficient  exactness  once  for  all  by 
closing,  with  a  piece  of  rubber  tubing  and  glass  rod, 
one  side  of  the  tube  filled  with  palladium,  cooling  the 
tube  to  about  9°  C.  by  placing  it  in  cool  water,  and 
then,  after  connecting  it  by  a  capillary  with  a  gas 
burette  completely  filled  with  water,  warming  it  to 
100°  by  placing  it  in  boiling  water.  The  expansion 
of  the  enclosed  air  volume  corresponds  to  a  difference 
of  temperature  of  91°,  i.e.  to  a  third  of  the  enclosed 
volume  of  gas.  Since,  however,  this  gas  which  has 
been  driven  over  is  measured  at  the  temperature  of 
the  room,  it  corresponds  to  only  about  a  fourth  of 
the  volume  of  the  palladium  tube.  It  is  important 
that  the  palladium  contain  no  water,  because  the 


CHAP,  iv          DETERMINATION   OF   HYDROGEN  189 

tension  of  water  vapour  would  cause  a  considerable 
error. 

The  palladium  is  regenerated  after  the  reaction  by 
first  leading  air  over  it,  whereby  it  becomes  quite 
hot ;  removing  any  drops  of  moisture  which  may 
collect,  so  that  the  palladium  may  easily  be  shaken 
out  of  the  tube  in  the  form  of  a  dry  powder  ;  and 
then  superficially  oxidising  the  metal  by  heating  it 
on  the  lid  of  a  platinum  crucible. 

The  residue  of  nitrogen  and  marsh-gas  which 
remains  after  the  absorption  of  the  hydrogen  is  burnt 
by  explosion  in  the  manner  to  be  later  described. 

With  the  aid  of  the  apparatus  here  mentioned,  the 
occlusion  of  hydrogen  by  palladium  may  be  very 


FIG.  78. 


strikingly  shown;  the  burette  is  filled  with  pure 
hydrogen  from  the  hydrogen  pipette,  and  is  then 
connected  with  the  pipette  by  means  of  a  glass  tube 
(Fig.  78)  in  which  2^  g.  of  palladium  sponge  con- 
taining some  palladious  oxide  are  enclosed,  a  and  b 
are  capillary,  and  <?,  which  contains  the  palladium,  is 
about  5  mm.  wide. 

Upon  leading  the  hydrogen  through  the  tube,  the 
absorption  begins  at  once  without  the  aid  of  external 
heat,  and  the  palladium  becomes  quite  hot ;  in  a 


190  GAS   ANALYSIS  PART  n 

very  short  time,  after  the  gas  has  been  passed  but  a 
few  times  back  and  to  through  the  palladium,  all 
of  the  hydrogen  disappears.  If  air  is  now  drawn 
through  the  palladium  by  means  of  a  bottle  aspirator 
or  any  similar  suction  arrangement,  the  hydrogen 
burns,  the  palladium  being  usually  seen  to  glow  at 
some  points  ;  the  palladious  oxide  necessary  for  the 
reaction  is  thus  formed,  and  the  tube  is  ready  for  a 
repetition  of  the  experiment. 

The  following  analyses  serve  as  illustrations  of 
this  method  of  absorption  :  — 

1.  Analyses  are  here  given  of  two  mixtures  of 
nitrogen  and  marsh-gas  made  at  different  times  and 
by  the  usual  method  from  sodium  acetate,  and  freed 
by  palladium  from  the  hydrogen  which  is  always 
simultaneously  given  off.  The  gases  contained,  be- 
fore the  absorption  with  palladium,  6.2  per  cent  of 
hydrogen.  The  analyses  were  made  over  mercury 
with  the  apparatus  for  exact  gas  analysis  described 
in  Part  I.  Chap.  IV.  B,  and  they  showed  that  it  is 
actually  possible  to  completely  free  marsh-gas  by 
means  of  palladium  from  any  hydrogen  which  it 
may  contain. 

The  nitrogen  of  the  mixture  comes  from  the  air 
which  was  not  thoroughly  driven  out  during  the 
evolution  of  the  gases,  and  in  the  present  analysis 
is  of  no  importance. 

The  combustion  analysis  gave  the  following 
results :  — 

I.   Marsh-gas  calculated  from  the  contraction  ....  52.45 

"  «  "         carbon  dioxide     .     .  52.3 

II.   Marsh-gas  calculated  from  the  contraction  ....  50.25 

"  "  "         carbon  dioxide     .     .  50.1 


CHAP,  iv          DETERMINATION   OF  HYDROGEN  191 

The  agreement  of  these  figures  is  quite  sufficient 
to  show  that  the  gases  must  be  regarded  as  mixtures 
of  marsh-gas  and  nitrogen  free  from  any  noticeable 
quantities  of  hydrogen. 

2.  Analyses  here  follow  of  artificial  mixtures  of 
hydrogen,  marsh-gas,   and   nitrogen,  the  marsh-gas 
being  previously  freed  from  any  hydrogen  it  might 
contain  by  means  of  palladium. 

(a)  27.2  ccm.  marsh-gas  and  nitrogen  mixed  with 

47.5  ccm.   hydrogen    gave,   after    absorption    with 
palladium  — 

27.2  ccm. 

(&)  27  ccm.  marsh-gas  and  nitrogen  mixed  with 

54.6  ccm.    hydrogen    gave,    after    absorption    with 
palladium  — 

27  corn. 

(<?)  13.3  ccm.  marsh-gas  and  nitrogen  mixed  with 
41.6  ccm.  hydrogen  gave,  after  absorption  with 
palladium  — 

13.3  ccm. 

3.  Four  analyses  of  Dresden  illuminating  gas  gave 
50.7,  50.6,  50.6,  50.6  per  cent  hydrogen.     The  mean 
of  several  explosion  analyses  was  50.5  per  cent. 

As  an  example  for  the  calculation,  the  following 
analysis  of  Dresden  illuminating  gas  (April  2, 
1879)  is  given.  The  direct  absorptions  gave  — 

3.5  per  cent  carbon  dioxide 
4.2       "         heavy  hydrocarbons 
0.2       "         oxygen 
10.6       "         carbon  monoxide. 


192  GAS   ANALYSIS  PART  n 

The  reading  after  absorption  with  palladium  gave 
a  decrease  of  volume  of  51.5  ccm. 

The  air  contained  in  the  palladium  tube  was  1.9 
ccm.,  hence  the  oxygen  therein  amounted  to  0.4  ccm. 

Since  this  oxygen  was  burned  during  the  reaction, 
the  volume  of  hydrogen  sought  is  51.5  —  0.4  =  51.1 
per  cent.  Of  the  gas  residue  of  marsh-gas  and  nitro- 
gen remaining  after  the  hydrogen  had  been  absorbed, 
15  ccm.  were  measured  off  in  a  burette  and  the  re- 
mainder was  kept  in  reserve  in  a  pipette. 

To  the  15  ccm.  of  gas  the  desired  quantity  of  air 
was  added  by  lowering  the  level-tube  and  opening 
the  pinchcock.  The  air  here  added  was  82.6  ccm. 
The  mixture  was  transferred  to  the  explosion  pipette, 
and  then  as  much  more  air  was  measured  off  in  the 
pipette  as  was  probably  necessary  for  the  complete 
combustion  of  the  gas  residue,  and  this  air  was  also 
brought  into  the  explosion  pipette. 

For  the  15  ccm.  of  gas  residue  of  marsh-gas  and 
nitrogen  160  ccm.  of  air  were  added;  in  other  words, 
the  second  portion  added  amounted  to  77.4  ccm. 

The  gases  were  thoroughly  mixed  in  the  pipette 
by  vigorous  shaking,  and  were  then  exploded.  After 
the  explosion  the  gas  was  led  into  the  caustic  potash 
pipette  to  absorb  the  carbon  dioxide  formed,  and  was 
then  measured. 

The  residue  was  more  than  the  burette  could  hold, 
and  on  this  account  it  was  measured  in  two  portions. 
Results :  — 

First  portion 97.5 

Second  portion 38.0 

Total  volume  after  explosion      .        .      135.5 


CHAP,  iv         DETERMINATION   OF   HYDROGEN  193 

Hence  the  contraction  was  — 
160  ccm.  +  15  ccm.  —  135.5  ccm.  =  39.5  ccm., 

which  corresponds  to  13. 2  ccm.  marsh-gas. 

Since  the  contents  of  the  palladium  tube  was  1.9 
ccm.,  and  the  volume  of  the  total  residue  of  marsh- 
gas  and  nitrogen  30.4  ccni.,  the  total  amount  of 
marsh-gas  is  given  by  the  proportion  — 

15  :  30.4  +  1.9  =  13.2  :  x. 
x  =  28.42  per  cent  marsh-gas. 

The  nitrogen  is  found  by  subtracting  the  sum  of  all 
the  constituents  from  100.  The  result  in  this  case  is  2. 
Hence  the  composition  of  the  gas  is  as  follows :  — 

3.5  per  cent  carbon  dioxide 

4.2  "  heavy  hydrocarbons 

0.2  "  oxygen 

10.6  "  carbon  monoxide 

51.1  "  hydrogen 

28.4  "  marsh-gas 

2.0  "  nitrogen. 

THE  ABSORPTION  OF  HYDROGEN  BY  POTASSIUM 
AND  SODIUM 

Jacquelain l  has  made  use  of  the  property  of  potas- 
sium of  absorbing  hydrogen  as  a  means  of  separating 
hydrogen,  marsh-gas,  and  ethylene. 

Potassium  and  sodium  can  be  melted  in  an  atmos- 
phere of  hydrogen  without  absorbing  the  gas.  The 
absorption  begins  at  200°  and  attains  its  maximum 
between  300°  and  400° ;  potassium  hydride  and  so- 
dium hydride,  substances  similar  to  silver  amalgam, 

1  Ann.  Chim.  Phys.  74,  203. 


194  GAS   ANALYSIS  PART  n 

are  formed.  These  compounds  can  be  melted  in 
vacuum  without  decomposition.  Heated  in  vacuum 
to  above  200°  they  give  up  hydrogen.  At  430°  the 
decomposition  in  vacuum  is  complete. 

Potassium  absorbs,  according  to  Troost  and  Haute- 
feuille,  124.6  volumes  of  hydrogen ;  sodium,  on  the 
other  hand,  23.8  volumes.  At  421°  the  absorption 
ceases,  unless  the  hydrogen  is  led  in  under  pressure. 

These  hydrogen  compounds  are  decomposed  by 
mercury,  with  formation  of  potassium  or  sodium 
amalgam.  These  amalgams  have  no  longer  the 
property  of  absorbing  hydrogen. 

The  author  has  repeatedly  endeavoured  to  work 
out  a  convenient  method  for  making  this  absorption. 

Mercury  forms  with  sodium  a  solid  amalgam,  and 
at  the  same  time  sets  free  again  any  hydrogen  with 
which  the  sodium  may  have  united,  while  petroleum 
begins  to  decompose  at  400°.  Hence  we  have  no 
confining  liquid  which  may  be  used  to  drive  the  gas 
completely  from  one  piece  of  apparatus  to  another. 

The  author  has  sought  to  use,  in  a  double  gas 
pipette,  the  alloy  of  potassium  and  sodium  which  is 
fluid  at  ordinary  temperatures,  as  confining  liquid, 
but  he  has  finally  come  to  the  conviction  that  this 
method  cannot  be  employed  because  of  the  fact  that 
the  slightest  trace  of  oxygen  or  moisture  causes  a 
stoppage  of 'the  capillary  by  the  formation  of  potas- 
sium or  sodium  oxide. 

Sodium  may  conveniently  be  used  for  determining 
hydrogen  if  the  gases  are  drawn  from  one  vessel  to 
another  by  means  of  a  small  Topler  air-pump  of  the 
form  used  by  the  author l  for  elementary  analysis. 

iFresenius,  Zeitschrift  fur  analytische  Chemie,  17,  409. 


CHAP,  iv     DETERMINATION   OF   NITROUS  OXIDE  195 

NITROUS  OXIDE  (N2O) 

Specific  gravity,  1.52269  ;  weight  of  1  liter, 
1.97023  ;  critical  temperature,  +35.4°  ;  critical  press- 
ure, 75  atmospheres ;  boiling-point  at  a  pressure  of 
one  atmosphere,  —87.2°;  specific  gravity  of  the 
liquid  gas,  0.9369. 

According  to  Carius,  nitrous  oxide  is  quite  soluble 
in  water.  One  volume  of  water  dissolves,  at  760  mm. 
pressure  and  20°,  0.670  volume. 

The  coefficient  of  absorption  is  — 

1.30521  -  0.045362 1  +  0.0006843 1*. 
For  alcohol  it  is  — 

4.17805  -  0.069816 1  +  0.000609  P, 

and  1  volume  of  alcohol  takes  up  at  20°  3.0253  vol- 
umes N2O. 

Bunsen  determines  nitrous  oxide  by  combustion 
with  hydrogen  and  oxyhydrogen  gas,  the  nitrous 
oxide  being  thereby  split  up  into  water  and  nitrogen. 
Since  this  is  a  purely  volumetric  method,  it  follows 
that  quantities  of  nitrous  oxide  which  are  less  than 
about  a  fifth  of  a  per  cent  of  a  gas  mixture  cannot  be 
thus  determined. 

The  idea  is  advanced  in  different  places  in  the 
literature  of  the  subject  that  this  method  is  not  exact 
because  of  accompanying  reactions. 

The  author  has  examined  the  method,1  and  has 
found  that  the  results  are  quite  satisfactory  if  the 
volume  of  hydrogen  is  two  to  three  times  that  of  the 
nitrous  oxide,  and  if  such  an  amount  of  oxyhydrogen 

1  Berichte  der  deutschen  chemischen  Gescllschaft,  1882,  p.  903. 


196  GAS   ANALYSIS  PART  n 

gas  is  added  that  to  100  volumes  of  incombustible 
gas  there  will  be  between  26  and  64  volumes  of  com- 
bustible gas.  The  combustion  is  made  in  the  explo- 
sion pipette.  The  decrease  of  volume  is  equal  to  the 
volume  of  the  nitrous  oxide. 

Two  volumes  of  nitrous  oxide  are  made  up  of  2 
volumes  of  nitrogen  and  1  volume  of  oxygen,  and 
require  for  combustion  2  volumes  of  hydrogen.  After 
the  combustion,  the  hydrogen  and  oxygen  have  dis- 
appeared, but  the  nitrogen  has  been  set  free,  hence 
the  contraction  is  equal  to  the  volume  of  nitrous 
oxide  sought.  Cl.  Winkler  has  proposed  1  to  deter- 
mine nitrous  oxide  by  leading  it  through  a  capillary 
in  which  a  palladium  wire  is  electrically  heated  to 
redness ;  the  volume  of  the  gas  is  thus  increased  one- 
half  :  — 

2N20  =  2N2+02, 
2  vol.  =  2  vol.  -f  1  vol. 

This  method  is,  however,  not  so  sharp  as  the  pre- 
ceding, because  the  change  of  volume  here  amounts 
to  only  one-half  of  the  volume  of  the  nitrous  oxide, 
while  in  the  combustion  this  change  is  as  large  as  the 
volume  of  the  N2O.  Special  chemical  absorbents  for 
nitrous  oxide  are  not  known. 

On  account  of  the  great  solubility  of  nitrous  oxide, 
contact  between  the  gases  to  be  analysed  and  aqueous 
solutions  must  be  avoided  as  far  as  possible. 

At  the  present  time  no  method  exists  for  detecting 
traces  of  nitrous  oxide. 


1  AnleUung  zur  chem.  Untersuchung  der  Industrie- Gase,  Part  II 
p.  427. 


CHAP,  iv     DETERMINATION  OF   NITRIC   OXIDE  197 

NITRIC  OXIDE  (NO) 

Specific  gravity,  1.03764 ;  weight  of  1  liter,  1.34261 ; 
critical  temperature,  —  93°  ;  critical  pressure,  71  at- 
mospheres ;  boiling-point  at  one  atmosphere  pressure, 
—  153.6°;  freezing-point,  —167°;  specific  gravity  of 
the  liquid  gas  at  its  critical  temperature,  1.039. 

The  coefficient  of  absorption  for  temperatures  be- 
tween 0°  and  25°  is,  according  to  Carius,  for  alcohol  — 

0.31606  -  0.003487  t  +  0.00004 1*. 

According  to  Oscar  Lubarsch1  nitric  oxide  is  ab- 
sorbed by  sulphuric  acid  of  varying  concentration  in 
the  following  amounts  :  — 

1.  100  parts  by  volume  H2SO4  absorb  3.5  volumes  NO. 

2.  100         "         «         (H2SO4+  2.5  H2O)  absorb  1.7  vol.  NO. 

3.  100         "         "         (H2SO4+  6.5  H2O)       "      2.0    "    NO. 

4.  100         «         «         (H2SO4+  9.0  H2O)       «      2.7    "    NO. 

5.  100         «         «         (H2SO4+17.0H2O)       "      4.5    «    NO. 

6.  100          "          "         water  absorb  7.2  vol.  NO. 

The  acids  mentioned  under  the  numbers  from  2  to 
5  have  the  following  percentage  strength :  — 

2.  68.5  per  cent  H2SO4. 

3.  45.5        «        H2S04. 

4.  37.7        «        H2SO4. 

5.  24.3        "        H2SO4. 

In  the  preceding  mixtures  there  are  used  2.5,  6.5, 
9.0,  and  17.0  equivalents  of  water  respectively  to 
one  equivalent  of  concentrated  sulphuric  acid. 

1  Oscar  Lubarsch's  Inaugural  Dissertation,  1886:  "A  new 
nitrometer  and  the  solubility  of  nitric  o^ide  in  sulphuric  acid," 


198  GAS  ANALYSIS  PART  n 

Nitric  oxide  cannot  be  determined  by  combustion 
with  hydrogen  because,  as  shown  by  the  researches 
of  Bunsen,  the  combustion  is  not  a  complete  one  ;  even 
when  the  explosion  is  quite  violent,  incomplete  com- 
bustion to  nitrous  oxide  takes  place. 

Nitric  oxide  is  determined  by  absorption  with  sol- 
utions of  ferrous  salts,  which  are  used  in  a  double 
pipette.  One  part  of  ferrous  sulphate  is  dissolved 
in  two  parts  of  water.  The  analytical  absorbing 
power  is  3. 

E.  Divers1  recommends  for  the  same  purpose  a 
concentrated  solution  of  sodium  or  potassium  sul- 
phite which  has  been  made  alkaline  by  the  addition 
of  some  potassium  hydroxide.  The  nitric  oxide  act- 
ing on  this  reagent  forms  a  hyponitrososulphate, 
Na2N202S03. 

Solutions  of  potassium  hydroxide  and  sodium 
hydroxide  do  not  absorb  nitric  oxide. 

The  nitric  oxide  present  in  a  current  of  gas  may 
be  determined  by  leading  the  gas  through  a  solution 
of  potassium  permanganate  acidified  with  sulphuric 
acid.  The  following  reaction  takes  place  :  — 

10  NO  +  6  KMnO4  +  9  H2SO4  = 

3  K2SO4  +  6  MnSO4  +  10  HNO3  +  4  H2O. 

NITEOGEN  TRIOXIDE  (N2O3) 

The  best  absorbent  for  nitrogen  trioxide  is  concen- 
trated sulphuric  acid  of  at  least  1.702  sp.  gr. 

Nitrogen  trioxide  is  easily  absorbed  by  alkaline 
solutions  with  formation  of  nitrites. 

i  Journ.  Chem.  Soc.  (London),  1899,  p.  82. 


CHAP,  iv  DETERMINATION   OF   AMMONIA  199 

Potassium  permanganate  absorbs  the  gas,  and  oxi- 
dises it  to  nitric  acid.  In  the  presence  of  sulphuric 
acid  the  reaction  is  — 

5  N2O3  +  4  KMnO4  +  6  H2SO4  = 

2  K2SO4  +  4  MiiSO4  +  10  HNO3  +  H2O. 

NITROGEN  TETROXIDE  (NO2) 

This  gas  is  actively  absorbed  by  alkaline  solutions 
and  by  sulphuric  acid.  By  potassium  permanganate 
it  is  changed  to  nitric  acid. 

10  N02  +  2  KMn04  +  3  H2SO4  +  2  H2O  = 

K2SO4  +  2  MnSO4  + 10  HNO3. 

AMMONIA  (NH3) 

Specific  gravity,  0.5889 ;  weight  of  IJiter,  0.76199; 
melting-point,  —78.3°;  boiling-point,  —33.7°,  spe- 
cific gravity  of  liquid  ammonia  at  0°  =  0.6233.  1 
volume  of  water  absorbs,  according  to  Bunsen,  — 

At  700  mm.  and    0° 1114.0 

645.2 

At  800  mm.  and    0° 1128.0 

«                «                  .....  701.7 

Alcohol  and  ether  also  absorb  considerable  quanti- 
ties of  the  gas. 

Measured  quantities  of  dilute  hydrochloric  or  sul- 
phuric acid  are  used  to  absorb  the  gas,  and  the  amount 
of  ammonia  is  determined  by  titrating  back  with  a 
standard  solution  of  an  alkali. 

If  a  direct  determination  is  not  possible,  as,  for 


200  GAS   ANALYSIS  PART  11 

instance,  in  gases  containing  large  amounts  of  tar, 
the  ammonia  may  be  absorbed  in  sulphuric  acid,  and 
the  nitrogen  present  may  then  be  set  free,  and  meas- 
ured in  a  Knop  azotometer. 

This  simple  and  very  exact  method  has  been  fur- 
ther worked  out  by  Wolf,  Dietrich,  P.  Wagner,  and 
F.  Soxhlet.1  It  is  based  upon  the  action  of  alkaline 
hypobro mites  upon  salts  of  ammonia,  all  nitrogen 
present  being  set  free. 

3  NaBrO  +  2  NH3  =  N2  +  3  H2O  +  3  NaBr. 

If  urea  is  present,  its  nitrogen  is  also  set  free. 

The  apparatus  necessary  for  making  this  determi- 
nation is  described  on  p.  72  (Fig.  41). 

In  carrying  out  the  analysis,  the  amount  of  nitro- 
gen actually  given  off  in  the  apparatus  under  the 
experimental  conditions  is  determined  by  using  a 
normal  ammonium  chloride  solution ;  in  the  second 
experiment,  the  liquid  in  question  is  put  into  0,  Fig. 
41.  The  difference  between  the  found  and  calculated 
amount  of  nitrogen  in  the  first  experiment  gives  a 
correction,  which  is  introduced  in  the  calculation  of 
the  results  from  unknown  amounts. 

METHYL- AMINE  (NH2.CH3) 

Specific  gravity,  1.13. 

1    volume  of  water  absorbs  at  12°  1040  volumes. 
1       "  "  "         25°    955         " 

It  condenses  at  a  temperature  somewhat  under  0°. 
It  is  absorbed  by  acids. 

1  Fresenius,  Quantitative  Analyse,  6th  ed.  Part  II,  pp.  681  and 
715. 


CHAP,  iv     DETERMINATION   OF   CARBON   DIOXIDE        201 

CARBON  DIOXIDE  (CO2) 

Specific  gravity,  1.51968;  weight  of  1  liter,  1.96633  ; 
critical  temperature,  31°  ;  critical  pressure,  77  atmos- 
pheres ;  boiling-point  at  pressure  of  1  atmosphere, 
-79.3. 

According  to  Bunsen  and  Pauli,  1  volume  of  water 
takes  up 

1. 7967  -  0.07761 1  +  0.0016424 12. 

1  ccm.  of  sulphuric  acid  (sp.  gr.  =  1.78)  dissolves 
at  14°  C.  and  816.4  mm.  pressure  1.16  ccm.  of  carbon 
dioxide. 

To  absorb  carbon  dioxide  either  potassium  hydrox- 
ide or  barium  hydroxide  is  used. 

For  volumetric  determinations  a  solution  of  1  part 
of  commercial  caustic  potash  in  2  parts  of  water  is 
employed.  Analytical  absorbing  power,  40  ccm. 
carbon  dioxide.  This  solution  is  put  into  the  simple 
pipette  for  solid  and  liquid  reagents  (Fig.  32),  the 
cylindrical  part  0  being  first  closely  filled  with  very 
short  rolls  of  iron  wire-gauze.  The  gauze  has  a  mesh 
of  1  to  2  mm.,  and  the  rolls  are  from  1  to  2  cm.  long 
and  about  5  mm.  thick. 

When  the  per  cent  of  carbon  dioxide  is  not  too 
high,  it  can  be  completely  absorbed  by  simply  passing 
the  gas  once  into  the  pipette.  The  complete  manip- 
ulation does  not  take  one  minute. 

Since  a  33  J  per  cent  solution  of  caustic  potash  is 
quite  viscous,  so  much  of  the  reagent  remains  hang- 
ing on  the  gauze  when  the  gas  is  introduced  that  on 
the  one  hand  the  absorption  of  the  carbon  dioxide 
takes  place  at  once,  and  on  the  other  hand  the  simul- 


202  GAS  ANALYSIS  PART  n 

taneous  absorption  of  oxygen,  caused  by  the  oxida- 
tion of  the  iron,  is  impossible,  because  the  gauze  is 
completely  protected  by  the  solution  from  the  action 
of  the  air,  as  repeated  experiments  have  shown. 

The  wire-gauze  has  a  further  advantage.  It  cools 
the  warm  gases  at  once  down  to  the  temperature  of 
the  room,  so  that  the  absorption  of  the  carbon  dioxide 
formed  in  the  combustion  of  marsh-gas  (see  later) 
may  also  be  very  suitably  made  in  the  carbon  dioxide 
pipette. 

Small  quantities  of  carbon  dioxide  are  best  deter- 
mined by  absorption  in  a  solution  of  barium  hydroxide 
and  titration  with  oxalic  acid. 

CARBON  MONOXIDE  (CO) 

Specific  gravity,  0.96709;  weight  of  1  liter,  1.25133; 
critical  temperature,  —  141° ;  critical  pressure,  35  at- 
mospheres ;  boiling-point  under  pressure  of  1  atmos- 
phere, —  190°  ;  freezing-point,  —207°.  1  volume 
of  water  dissolves,  according  to  Bunsen,  — 

0.032874  -  0.00081632 1  +  0.000016421 1* 
volume  of  carbon  monoxide ;  hence  at 
20°,  0.02312. 

According  to  Carius,  alcohol  dissolves  between  0° 
and  25°,  0.20443  volume  CO. 

For  absorbing  carbon  monoxide,  either  an  ammo- 
niacal  or  a  hydrochloric  acid  solution  of  cuprous 
chloride  is  used. 

The  hydrochloric  acid  solution  of  cuprous  chloride 
may  be  prepared,  according  to  Winkler,  by  adding 


CHAP,  iv    DETERMINATION   OF   CARBON  MONOXIDE     203 

a  mixture  of  86  g.  of  copper  oxide  and  17  g.  of  finely 
divided  metallic  copper  to  1086  g.  of  hydrochloric 
acid  (sp.  gr.  =  1.124),  the  mixture  being  slowly 
introduced  and  the  acid  frequently  stirred.  The 
copper  powder  is  best  prepared  by  the  reduction  of 
copper  oxide  with  hydrogen.  After  this  mixture  has 
been  introduced  into  the  acid,  a  spiral  of  copper 
wire  reaching  from  the  bottom  of  the  bottle  up  to 
its  neck  is  inserted  and  the  bottle  is  closed  with  a 
soft  rubber  stopper.  The  solution  is  dark  in  the 
beginning,  but  upon  standing  it  becomes  wholly 
colourless.  In  contact  with  the  air,  however,  it  again 
turns  dark  brown,  and  some  cupric  chloride  forms. 

The  analytical  absorbing  power  of  the  solution  is 
4  ccm.  of  carbon  monoxide. 

Another  method  somewhat  more  rapid  and  con- 
venient than  that  just  described  is  given  by  Sand- 
meyer.1 

25  parts  of  crystallized  copper  sulphate  and  12 
parts  of  dry  sodium  chloride  are  placed  in  50  parts 
of  water  and  heated  until  the  copper  sulphate  dis- 
solves. Some  sodium  sulphate  may  separate  out  at 
this  point,  but  the  preparation  is  continued  without 
the  removal  of  this  salt.  100  parts  of  concentrated 
hydrochloric  acid  and  13  parts  of  copper  turnings 
are  then  added  and  the  whole  is  boiled  in  a  flask 
until  decolourised.  To  avoid  excessive  evaporation 
it  is  desirable  to  insert  in  the  neck  of  the  flask  a  tall 
condensing  tube  or  an  upright  condenser.  The 
addition  of  platinum  foil  to  the  contents  of  the  flask 
will  facilitate  reduction.  The  solution  should  be 

1  Serichte  der  deutschen  chemischen  Gesellschaft  17,  1633. 


204  GAS  ANALYSIS  PART  n 

kept  in  bottles  which  are  filled  up  to  the  neck  and 
are  closed  by  rubber  stoppers. 

The  ammoniacal  solution  of  cuprous  chloride  is 
prepared  (the  amounts  here  given  make  200  com.)  by 
dissolving  10.3  g.  of  copper  oxide  in  100  to  200  com. 
of  concentrated  common  hydrochloric  acid,  and  then 
allowing  the  solution  to  stand  in  a  flask  of  suit- 
able size,  filled  as  full  as  possible  with  copper  wire 
or  copper  wire-gauze,  until  the  cupric  chloride  is 
reduced  to  cuprous  chloride,  and  the  solution  is 
completely  colourless.  The  clear  hydrochloric  acid 
solution  thus  prepared  is  poured  into  a  large  beaker 
glass  or  cylinder  containing  1J  to  2  liters  of  water, 
to  precipitate  the  cuprous  chloride  formed.  After 
the  precipitate  has  settled,  the  dilute  hydrochloric 
acid  is  poured  off  as  completely  as  possible,  the  cu- 
prous chloride  is  then  washed  into  a  250  ccm.  flask  with 
about  100  to  150  ccm.  of  distilled  water,  and  ammonia 
is  led  into  the  solution,  which  is  still  slightly  acid, 
until  the  liquid  takes  on  a  pale  blue  colour.  Since 
the  tension  of  very  concentrated  ammonia  solutions 
renders  the  absorption  difficult,  no  more  ammonia 
than  is  necessary  should  be  added.  While  the 
ammonia  is  being  led  in,  it  is  well  to  protect  the 
contents  of  the  flask  from  the  oxidising  influence  of 
the  air.  This  may  be  done  by  providing  the  flask 
containing  the  cuprous  chloride  to  be  dissolved,  with 
a  double-bored  stopper  through  one  opening  of  which 
passes  the  delivery  tube  from  the  ammonia  flask, 
while  through  the  other  opening  is  inserted  a  bent 
glass  tube  that  dips  into  a  little  mercury.  If  a  flask 
with  a  funnel -tube  is  used  for  the  evolution  of  am- 
monia, hydrogen  may  first  be  led  through  this  tube, 


CHAP,  iv    DETERMINATION   OF  CARBON   MONOXIDE    205 

and  the  apparatus  be  thus  completely  freed  from 
air.  For  the  evolution  of  ammonia  about  200  ccm. 
of  a  concentrated  ammonia  solution  of  0.9  sp.  gr.  is 
used. 

The  solution  of  cuprous  chloride  thus  prepared  is 
diluted  with  water  to  200  ccm.,  and,  since  the  hydro- 
chloric acid  was  not  entirely  washed  out,  there  is  of 
course  some  ammonium  chloride  present.  100  ccm. 
contains  7.3  g.  of  cuprous  chloride. 

The  analytical  absorbing  power  of  this  solution  is 
6  ccm.  of  carbon  monoxide. 

It  is  quite  impracticable  to  use  more  dilute  solu- 
tions of  cuprous  chloride. 

The  following  method  for  the  preparation  of  an 
ammoniacal  solution  of  cuprous  chloride  will  be  found 
convenient.  1  liter  of  the  hydrochloric  acid  solution 
prepared  by  the  Winklcr  method  given  above  or 
1500  cc.  of  the  Sandmeyer  solution  is  poured  into 
about  5  liters  of  water,  and  the  resulting  precipitate  is 
transferred  to  a  stoppered  measuring  cylinder  con- 
taining about  320  ccm.  and  upon  which  there  has 
previously  been  marked  the  height  at  which  62  ccm. 
of  liquid  would  stand.  After  about  two  hours  the 
precipitate  and  liquid  which  is  above  this  62  ccm.  mark 
is  drawn  off  by  means  of  a  siphon  and  7.5  per  cent 
ammonium  hydroxide  is  added  up  to  the  320  ccm. 
mark,  that  is,  to  the  top  of  the  cylinder.  The  stopper 
is  inserted,  the  cylinder  is  well  shaken,  and  it  is  then 
allowed  to  stand  for  several  hours.  A  solution  pre- 
pared in  this  manner  has  so  slight  a  tension  that  the 
latter  may  in  nearly  every  case  be  neglected. 

If,  after  the  absorption  of  the  carbon  monoxide  in 
a  gas  mixture,  the  hydrogen  is  to  be  determined  with 


206  GAS  ANALYSIS  PART  n 

palladium,  the  ammoniacal  solution  must  be  used.  If 
the  amount  of  carbon  monoxide  alone  is  to  be  ascer- 
tained, the  hydrochloric  acid  solution  may  be  em- 
ployed with  equally  good  results.  These  solutions 
of  cuprous  chloride  are  used  in  the  double  pipette 
(Fig.  33). 

H.  Drehschmidt1  has  shown,  however,  that  the 
union  of  carbon  monoxide  with  cuprous  chloride  is  so 
feeble  that  upon  shaking  a  solution  which  has  taken 
up  any  considerable  quantity  of  carbon  monoxide, 
this  gas  is  again  given  up  in  an  atmosphere  free  from 
carbon  monoxide.  For  this  reason  two  pipettes  are 
used  in  the  absorption,  one  pipette  containing  a 
frequently  used,  the  other  a  but  slightly  used,  solution 
of  cuprous  chloride.  In  the  absorption,  the  gas  in 
question  is  first  shaken  for  two  minutes  with  the  first- 
mentioned  solution,  and  is  then  transferred  to  the 
second  pipette  containing  the  but  slightly  used  solu- 
tion, and  is  shaken  three  minutes  therein.  Accord- 
ing to  Drehschmidt,  the  ammoniacal  solution  is  to  be 
preferred  to  the  hydrochloric  acid  one. 

Solutions  of  cuprous  chloride  have  no  considerable 
tension,  so  that  this  may  be  disregarded  in  analyses 
which  are  to  give  only  approximate  results,  or  in 
which  no  great  accuracy  is  necessary.  In  exact 
determinations,  however,  the  gases  which  have  been 
in  contact  with  the  reagent  must  be  freed  from  the 
gaseous  hydrochloric  acid  or  from  the  ammonia ;  this 
can  be  brought  about  in  the  burette  itself,  or  in  a 
pipette  filled  with  distilled  water. 

The  solutions  of  cuprous  chloride  are  thin,  and 

1  Berichte  der  deutschen  chemischen  Gesellschaft,  20,  2344 ;  20, 
2752  ;  and  21,  2158. 


CHAP,  iv    DETERMINATION  OF   CARBON  MONOXIDE    201 

they  flow  readily;  hence  it  is  unadvisable  to  make 
the  absorption  in  the  double  pipette  for  solid  and 
liquid  reagents  (Fig.  34),  in  which  the  cylinder  a 
has  been  filled  with  copper  wire-gauze,  for  the  absorp- 
tion is  not  here  effected,  as  with  carbon  dioxide,  by 
simply  leading  the  gas  once  into  the  pipette ;  on  the 
contrary,  it  can  be  brought  about  only  after  some 
time  by  frequently  repeating  this  operation.  . 

The  solutions  of  cuprous  chloride  are  absorbents 
not  only  for  carbon  monoxide  and  acetylene,  but  also 
for  ethylene  —  a  fact  which  is  not  taken  into  account 
in  a  number  of  gas  analyses  lately  published,  and  the 
disregard  of  which  must  of  course  lead  to  wholly  use- 
less results. 

The  author  was  unable  to  find  any  notice  of  this 
particular  in  the  existing  literature,  and  by  the  recur- 
rence of  an  error  in  an  analysis  of  illuminating  gas 
he  was  led  to  investigate  the  behaviour  of  cuprous 
chloride  toward  ethylene.  He  at  first  believed  that 
marsh-gas  was  somewhat  soluble  in  cuprous  chloride, 
but  further  experiments  showed  that  this  was  not  the 
case. 

To  study  the  action  of  ethylene  toward  cuprous 
chloride,  25  parts  by  weight  of  absolute  alcohol  were 
mixed  with  150  parts  by  weight  of  concentrated 
sulphuric  acid,  and  the  gas  given  off  upon  careful 
heating  was  passed,  first  through  an  empty  bottle, 
and  then  through  concentrated  sulphuric  acid  and 
through  several  wash-bottles  filled  with  a  concentrated 
solution  of  potassium  hydroxide.  After  the  evolution 
of  gas  had  gone  on  for  an  hour,  the  gas  was  collected 
in  a  small  glass  gasometer  over  a  strongly  alkaline 
solution  of  pyrogallol,  and  was  analysed  after  stand- 


208  GAS  ANALYSIS  PART  n 

ing  for  several  days.  91.3  per  cent  of  the  gas  was 
absorbable  by  concentrated  sulphuric  acid. 

Another  portion  of  the  gas,  brought  together  with 
a  hydrochloric  acid  solution  of  cuprous  chloride,  gave 
94.3  per  cent  of  absorbable  gas. 

Another  sample  of  ethylene  prepared  by  the  same 
method  gave,  in  two  experiments  with  hydrochloric 
acid  cuprous  chloride,  94.5  per  cent  of  absorbable 
constituents. 

In  two  experiments  with  ammoniacal  cuprous 
chloride,  95.0  per  cent  of  absorbable  constituents. 

The  last  four  analyses  were  not  made  in  pipettes, 
but  in  the  simple  gas  burette  with  unsaturate.d 
reagent.  The  difference  in  the  results  is  caused  by 
the  different  solubility  of  nitrogen  in  ammoniacal  and 
hydrochloric  acid  cuprous  chloride  ;  and  it  is  as  large 
as  it  is  because  the  residual  5  ccm.  of  gas  in  the 
analysis  came  into  intimate  contact  with  95  ccm.  of 
unsaturated  absorbing  liquid. 

In  the  method  of  preparing  ethylene  described 
above,  some  carbon  is  always  separated,  and  this, 
upon  being  heated  with  sulphuric  acid,  gives  off 
carbon  monoxide  in  addition  to  sulphur  dioxide  and 
carbon  dioxide  The  presence  of  the  carbon  monox- 
ide completely  explains  why  the  cuprous  chloride  ab- 
sorbed 3  per  cent  more  gas  than  the  fuming  sulphuric 
acid. 

Certain  analytical  data  indicate  that  the  heavy 
hydrocarbons  are  not  equally  absorbable  by  the  re- 
agent. Ethylene  appears  to  be  absorbed  with  especial 
ease.  It  remains,  therefore,  to  ascertain  whether 
cuprous  chloride  itself  cannot  be  used  for  separating 
the  heavy  hydrocarbons. 


CHAP,  iv     DETERMINATION  OF   CARBON   MONOXIDE    209 

Preliminary  experiments  showed  further,  that  the 
gases  not  absorbable  by  cuprous  chloride  are  much 
more  soluble  in  this  reagent  than  in  other  absorbing 
liquids.  This  fact  shows  that,  to  obtain  accurate 
results,  a  cuprous  chloride  solution  which  has  been 
saturated  with  the  gases  but  slightly  soluble  in  it 
must  unquestionably  be  used. 

In  the  three  determinations,  given  later,  of  carbon 
monoxide  in  an  illuminating  gas  from  which  the 
carbon  dioxide,  heavy  hydrocarbons,  and  oxygen  had 
been  absorbed,  8.6  and  8.5  per  cent  of  carbon  monox- 
ide was  found  with  unsaturated  reagent,  and  8.1  per 
cent  with  reagent  which  had  been  saturated  by  re- 
peated use,  but  which  still  possessed  high  absorbing 
power. 

These  experiments  showed  further  that  the  cuprous 
chloride  solution  is  not  suited  to  the  absorption  of 
oxygen,  since  complete  absorption  is  attained  only 
after  shaking  for  a  very  long  time.  The  gases  to  be 
treated  with  this  reagent  must  on  this  account  be 
free  from  oxygen. 

•  The  author  has  also  found  that  the  hydrochloric 
acid  solution  of  cuprous  chloride  is  not  changed  by 
petroleum,  so  that  this  reagent  may  be  kept  under 
petroleum  in  a  bottle  having  at  the  bottom  a  tubulus 
and  stopcock ;  the  bottle  should  be  completely  filled 
and  tightly  stoppered.  If,  after  some  cuprous 
chloride  has  been  take'n  out,  the  bottle  is  kept  full 
of  petroleum  and  tightly  closed,  the  solution  does 
not  change  in  strength. 

In  May,  1885,  Mr.  Karl  Markel,  chemist  of  the 
Ammonia-soda  Works  at  Wilmington,  England, 
called  the  author's  attention  to  the  fact  that  in  the 


210  GAS  ANALYSIS  PART  n 

absorption  of  carbon  monoxide  with  cuprous  chloride, 
the  gas  volume  at  times  did  not  decrease,  but  on  the 
contrary  became  considerably  greater.  He  sent  a 
number  of  analyses  of  generator  gases  in  confirmation 
of  his  statement.  In  none  of  these  analyses  were  the 
heavy  hydrocarbons  determined  either  by  fuming 
sulphuric  acid  or  any  other  reagent,  so  that  it  was 
surmised  that  these  gases  might  be  the  cause  of  the 
irregularity.  Experiments  have  borne  out  this 
assumption,  and  have  shown  that  even  when  the 
determination  of  the  heavy  hydrocarbons  is  of  no 
importance  for  the  analysis,  they  must,  nevertheless, 
be  removed  before  the  carbon  monoxide  is  absorbed 
with  cuprous  chloride. 

If  ethylene  is  absorbed  with  cuprous  chloride,  and 
this  solution  is  then  used  for  the  absorption  of  carbon 
monoxide,  a  certain  quantity  of  ethylene  is  set  free, 
so  that  the  results  of  the  analysis  are  of  course  erro- 
neous. If  the  same  solution  of  cuprous  chloride  is 
used  for  a  large  number  of  absorptions,  the  case  may 
arise  that  the  gas  volume  does  not  decrease  when  the 
carbon  monoxide  is  absorbed,  but  on  the  contrary  is 
increased  by  the  ethylene  set  free.  It  is  obvious  that 
an  increase  of  volume  may  also  be  caused  by  carbon 
monoxide  being  set  free  in  the  manner  mentioned  by 
Drehschmidt. 

Cl.  Winkler l  has  found  that  if  palladious  chloride 
be  added  to  solutions  of  cuprous  chloride  in  hydro- 
chloric acid,  ammonium  chloride,  or  sodium  chloride, 
then  these  solutions,  if  they  have  absorbed  carbon 
monoxide,  give  upon  dilution  with  water  a  precipitate 

A  Fresenius,  Zeitschrift  fur  analyt.  Chemie,  28,  269. 


CHAP,  iv    DETERMINATION  OF   CARBON   MONOXIDE    211 

of  metallic  palladium,  the  carbon  monoxide  being  at 
the  same  time  oxidised  to  carbon  dioxide. 

F.  P.  Treadwell  and  H.  N.  Stokes1  have  shown 
that  carbon  monoxide  can  be  completely  absorbed 
with  fuming  nitric  acid,  if  the  two  are  shaken 
together  for  quite  a  long  time  (25  minutes). 

Small  quantities  of  carbon  monoxide  may  be  de- 
tected by  means  of  blood.  H.  W.Vogel2  was  the 
first  to  use  the  well-known  spectrum  reaction  of  blood 
impregnated  with  carbon  monoxide,  as  a  means  of 
finding  small  amounts  of  the  gas.  This  reaction  is 
of  especial  significance,  because  the  carbon  monoxide 
cannot  be  confounded  with  another  gas  —  a  fact 
which,  on  account  of  the  highly  poisonous  character 
of  the  substance,  is  of  great  importance  in  analyses 
undertaken  from  a  sanitary  standpoint. 

To  detect  carbon  monoxide,  Vogel  directs  that  a 
100  ccm.  bottle,  filled  with  water,  be  emptied  in  the 
room  containing  the  gas,  and  that  2  to  3  ccm.  of  blood, 
highly  diluted  with  water,  and  showing  only  a  very 
faint  red  colour,  yet  still  giving  the  well-known  ab- 
sorption bands  of  oxyhsemoglobin  (see  Fig.  79,  spec- 
trum No.  2)  in  a  column  as  thick  as  a  test-tube,  be 
poured  into  the  bottle  and  shaken  for  some  minutes. 
When  carbon  monoxide  is  present,  the  blood  at  once 
takes  on  a  rose  colour,  the  absorption  bands  shift 
slightly  toward  the  violet,  and  the  spectrum  of  carbon 
monoxide  haemoglobin  appears  (Spectrum  No.  3). 
When  a  few  drops  of  strong  ammonium  sulphide  are 
added  to  this  solution  the  absorption  bands  do  not 
disappear,  but  on  the  contrary,  maintain  their  posi- 

1  Serichte  der  deutschen  chemischen  Gesellschaft,  1888,  p.  3131. 

2  Ibid.  11,  235 ;  also  10,  792. 


212 


GAS   ANALYSIS 


PART  n 


tion.  If,  however,  no  carbon  monoxide  has  come 
into  contact  with  the  blood,  the  bands  due  to  the 
oxy haemoglobin  (Spectrum  No.  2)  disappear  and  are 
replaced  by  a  broad  and  weakly  defined  band  (Spec- 
trum No.  4). 

BC       D          E6        F  G 

Pure  blood  highly  diluted 


Blood  highly  diluted  +  CO 

Blood  highly  diluted 

+  NH4SH 


FIG.  79. 


Vogel  states  that  amounts  down  to  0.25  per  cent 
can  be  clearly  detected,  but  that  the  delicacy  is  not 
increased  by  using  greater  volumes  of  air. 

The  author  found  by  experiment  that  it  was  not 
possible,  in  a  Liebig  potash-bulb  or  by  shaking,  to 
completely  remove  very  small  amounts  of  carbon  mon- 
oxide from  a  gas  mixture  by  means  of  an  exceedingly 
dilute  solution  of  blood,  such  as  Vogel  employs ;  and 
he  also  found  that  concentrated  solutions  of  blood 
could  not  be  used  because  they  foam  so  much.  He 
was  thus  led  to  the  idea  that  by  using  living  animals, 
whose  lungs  would  furnish  an  absorption  apparatus 
of  incomparable  completeness  and  admit  of  the  use 
of  undiluted  blood,  it  might  be  possible  to  still 
further  increase  the  delicacy  of  the  reaction. 

This  supposition  was  proved  correct  by  the  experi- 
ments which  follow,  and  it  led  to  a  more  delicate 
method  for  detecting  carbon  monoxide. 


CHAP,  iv    DETERMINATION  OF   CARBON  MONOXIDE     213 

Mice  were  used  in  the  work,  and  they  were  exposed 
to  the  action  of  the  gas  to  be  tested  for  carbon  mon- 
oxide by  placing  them  between  two  funnels  joined 
together  at  the  mouths  by  means  of  a  broad  band  of 
thin  rubber.  The  ends  of  the  funnels  were  connected 
to  the  gasometers  and  absorption  apparatus  by  pieces 
of  rubber  tubing. 

To  bring  the  mouse,  without  hurting  it,  into  this 
simple  apparatus,  the  animal  is  first  dropped  into  a 
large  and  wide  glass  cylinder.  It  is  then  covered 
with  one  of  the  funnels,  a  glass  plate  is  slipped  under 
the  funnel,  and  the  mouse  is  lifted  out.  The  mouth 
of  the  second  funnel  is  then  brought  opposite  that  of 
the  first  one,  the  glass  plate  is  drawn  out,  and  the 
funnels  are  joined  together  by  the  rubber  band. 

Mixtures  of  air  and  carbon  monoxide  were  used  in 
the  experiments.  The  carbon  monoxide  was  made 
with  great  care,  either  from  potassium  ferrocyanide 
and  sulphuric  acid,  or  from  oxalic  acid  and  sulphuric 
acid,  and  was  washed  with  a  sodium  hydroxide  solu- 
tion. The  lighter  carbon  monoxide  was  led  into  the 
air  from  below,  and  the  mixture  was  allowed  to  stand 
and  diffuse  for  at  least  twelve  hours. 

The  current  of  gas  was  so  regulated  that  10  liters 
of  gas  passed  through  the  apparatus  in  from  one  to 
two  hours,  and  the  gases  coming  from  the  funnels 
contained  from  0.3  to  2.8  per  cent  of  carbon  dioxide, 
resulting  from  the  respiration  of  the  mouse.  Fre- 
quently repeated  analyses  showed,  however,  that  this 
carbon  dioxide  did  not  usually  rise  above  1  per  cent, 
so  that  it  was  impossible  for  it  to  cause  any  seriously 
injurious  results. 

In  some  experiments  also,  as  is  described  in  detail 


214  GAS   ANALYSIS  PART  n 

below,  a  Liebig  potash-bulb  filled  with  a  fresh  blood 
solution,  which  was  highly  diluted  according  to 
Vogel's  directions,  was  placed  either  before  or  after 
the  animal. 

The  mice  were  killed  by  immersing  the  funnels 
in  water,  and  a  considerable  quantity  of  blood  was 
obtained  by  cutting  them  in  two  in  the  region  of  the 
heart. 

The  detection  of  the  carbon  monoxide  haemoglobin 
was  always  carried  out  with  a  freshly  prepared  solu- 
tion of  colourless  ammonium  sulphide ;  and  to  con- 
trol the  results,  fresh  blood  of  the  same  dilution  and 
free  from  carbon  monoxide  was  treated  with  the 
same  amount  of  ammonium  sulphide.  To  obtain 
this  fresh  blood  a  mouse  which  had  not  been  in 
contact  with  carbon  monoxide  was  killed  shortly 
before  the  experiment. 

To  still  further  control  the  results,  the  author  also 
used  in  most  of  the  experiments  freshly  prepared 
ammonium  ferrous  tartrate,  with  the  same  success  as 
with  the  ammonium  sulphide.  But  the  preference 
must  be  given  to  the  colourless  ammonium  sulphide, 
because,  when  that  is  used,  a  difference  in  the  colours 
of  the  reduced  solutions  when  traces  of  carbon  mon- 
oxide are  present,  is  quite  easily  distinguishable  even 
without  the  aid  of  the  spectroscope.  The  liquid  con- 
taining the  carbon  monoxide  hsemoglobin  is  more 
distinctly  red  in  colour. 

A  Vogel  "universal  spectroscope,"  made  by  Schmidt 
and  Haensch,  was  used  for  observing  the  spectra. 

Experiment  1. — The  gas  contained  0.022  per 
cent  carbon  monoxide.  Before  the  animal  there 
was  placed  an  absorption  apparatus  containing  blood. 


CHAP,  iv    DETERMINATION  OF  CARBON  MONOXIDE    215 

The  mouse  showed  no  symptoms  of  poisoning.  Ex- 
periment was  stopped  at  the  end  of  three  hours. 

Carbon  monoxide  could  be  detected  neither  in  the 
mouse  nor  in  the  interposed  blood. 

Experiment  2. —  Gas  contained  0.032  per  cent  of 
carbon  monoxide.  No  absorption  apparatus  contain- 
ing blood  was  placed  before  the  animal. 

The  mouse  showed  no  symptoms  of  poisoning. 
Experiment  was  stopped  at  the  end  of  three  hours. 

The  blood  of  the  mouse  gave  a  weak  but  unmis- 
takable reaction  for  carbon  monoxide. 

Experiment  3. —  Gas  contained  0.032  per  cent  of 
carbon  monoxide.  Only  an  absorption  apparatus 
containing  a  dilute  blood  solution  was  used. 

Carbon  monoxide  could  not  be  detected.  Consider- 
able albumen  was  coagulated,  so  that  the  solution, 
which  previously  had  been  clear,  was  now  turbid. 

Experiment  4. — Gas  contained  0.043  per  cent  of 
carbon  monoxide.  The  mouse  showed  no  symptoms 
of  poisoning.  Experiment  was  stopped  at  the  end  of 
four  hours.  Distinct  reaction  for  carbon  monoxide. 
Even  without  the  aid  of  the  spectroscope,  the  presence 
of  carbon  monoxide  could  be  clearly  recognised  from 
the  red  tone  of  the  reduced  blood. 

Experiment  5.  —  Gas  contained  0.067  per  cent  car- 
bon monoxide.  An  absorption  apparatus  containing 
blood  was  interposed  before  the  animal. 

After  half  an  hour  slight  symptoms  of  poisoning  — 
difficult  respiration — could  be  seen.  After  three 
hours  the  experiment  was  stopped. 

In  the  mouse  the  carbon  monoxide  could  be  plainly 
detected ;  the  blood  solution  also  gave  the  reaction, 
but  much  more  faintly. 


216  GAS  ANALYSIS  PART  n 

Experiment  6.  —  Gas  contained  0.0593  per  cent  of 
carbon  monoxide.  An  absorption  apparatus  contain- 
ing blood  was  placed  after  the  mouse. 

After  half  an  hour  unmistakable  symptoms  of 
poisoning  showed  themselves  —  the  mouse  breathed 
with  difficulty  and  lay  exhausted  on  its  side.  The 
experiment  was  stopped  at  the  end  of  47J  minutes. 
Carbon  monoxide  in  the  animal  could  be  clearly 
recognised,  but  less  plainly  in  the  blood  solution. 

Experiment  7. —  Gas  contained  0.127  per  cent  of 
carbon  monoxide.  An  absorption  apparatus  contain- 
ing blood  was  placed  before  the  animal. 

At  the  end  of  only  seven  minutes  there  were  strong 
symptoms  of  poisoning.  The  interposed  blood  solu- 
tion, as  well  as  the  blood  of  the  mouse,  gave  the 
reaction  for  carbon  monoxide  at  the  end  of  two 
hours. 

Experiment  8.  —  Gas  contained  2.9  per  cent  of 
carbon  monoxide.  In  from  one  to  two  minutes  the 
mouse  died  with  convulsions.  The  blood  gave  a 
strong  carbon  monoxide  reaction. 

This  last  experiment  shows  vividly  the  frightfully 
poisonous  action  of  carbon  monoxide,  for  a  few  cubic 
centimeters  of  the  still  very  dilute  carbon  monoxide 
suffice  to  produce  at  once  strong  symptoms  of  poison- 
ing in  a  mouse. 

Taking  the  results  as  a  whole,  we  see  — 

(1)  That  when  large  volumes  of  gas  (at  the  least 
10  liters)  are  used,  amounts  of  carbon  monoxide  down 
to  0.05  per  cent  can  be  easily  and  certainly  detected 
either   by   using   dilute    blood   or   a   living   animal 
(a  mouse). 

(2)  That  the  limit  of  the  test  lies  at  about  0.03 


CHAP,  iv    DETERMINATION   OF   CARBON  MONOXIDE    217 

per  cent  when  a  mouse  is  used,  and  with  dilute  blood 
at  about  0.05  per  cent. 

(3)  That  decided  symptoms  of  poisoning  are  ob- 
served from  0.05  per  cent  upward. 

The  author  is  accordingly  of  the  opinion  that,  to 
examine  the  air  of  a  room  for  carbon  monoxide, 
either  the  Vogel  test  must  be  used,  a  few  cubic 
centimeters  of  very  dilute  blood  being  placed  in  an 
absorption  apparatus  and  10  liters  of  air,  at  the  least, 
being  led  through  it,  or,  as  is  more  convenient  in 
many  cases  and  also  more  delicate,  that  a  mouse 
placed  in  an  ordinary  wire  trap  be  allowed  to  breathe 
the  air  of  the  room  for  some  hours,  and  the  blood  of 
the  animal  be  then  examined. 

Vogel,1  and,  later,  Gustav  Wolffhiigel,  in  his  very 
interesting  article  upon  "  carbon  monoxide  and  cast- 
iron  stoves,"2  state  that  in  their  opinions  quantities 
of  carbon  monoxide  smaller  than  0.25  per  cent — the 
limit  of  the  delicacy  of  the  Vogel  test  when  100  ccm. 
of  air  is  used  —  may  be  disregarded  from  a  hygienic 
standpoint,  and  they  would  regard  the  presence  of 
traces  of  carbon  monoxide  in  the  air  of  a  room  in  the 
same  light  as  one  looks  upon  the  presence  of  organic 
substances,  of  nitric  acid,  etc.,  in  drinking  water,  or 
of  carbon  dioxide  in  the  atmosphere.  But,  in  the 
opinion  of  the  author,  this  view  cannot  be  accepted 
when  we  take  into  consideration  the  foregoing  ex- 
periments, and  the  fact  also  that  carbon  monoxide 
does  not  belong,  as  does  carbon  dioxide,  to  the  un- 
avoidable constituents  of  the  air  of  a  room.  More- 
over, in  inspecting  heating  arrangements,  the  presence 

1  Berichte  der  deutschen  chemischen  Gesellschaft,  11,  236. 

2  Zeitschrift  fur  Biologie,  14,  506. 


218 


GAS  ANALYSIS 


PART  II 


of  any  carbon  monoxide  should,  from  a  sanitary  stand- 
point, be  regarded  as  inadmissible,  this  judgment 
being  wholly  independent  of  the  statement  that 
there  must  be  a  lower  limit  at  which  carbon  monox- 
ide has  no  poisonous  action  on  the  human  organism. 


FIG.  80. 

C.  H.  Wolff1  has  constructed  a  very  effective 
absorption  apparatus  adapted  to  the  use  of  small 
amounts  of  blood.  He  describes  it  as  follows :  — 

"  It  corresponds  essentially  to  the  De  Koninck 
modification  of  Mitscherlich's  absorption  apparatus, 
the  difference  being  that  at  #,  6,  and  e  (Fig.  80)  the 
tubes  are  closed  by  ground-glass  stoppers,  and  that 

1  Correspondenzblatt  des  Vereins  analytischer  Chemiker,  1880, 
3,46. 


CHAP,  iv    DETERMINATION   OF  CARBON   MONOXIDE    219 

the  cylinder  is  narrowed  at  d.  In  filling  the  appara- 
tus, a  little  wad  of  glass-wool  is  inserted  into  d  from 
above,  and  gently  pressed  into  place,  and  the  remain- 
der of  the  tube  as  far  as  /  is  then  filled  with  moder- 
ately fine  powdered  glass.  This  powdered  glass  is 
about  as  fine  as  ordinary  gunpowder.  It  is  freed 
from  any  fine  powder  and  dust  by  sifting,  and  is 
then  digested  with  hydrochloric  acid,  and  carefully 
washed  and  dried.  The  great  extent  to  which  the 
size  of  these  grains  adds  to  the  power  of  absorption 
through  increase  of  surface  is  shown  by  the  interest- 
ing researches  of  Dr.  Soyka  in  Prague,  upon  the  influ- 
ences of  the  soil  upon  the  decomposition  of  organic 
substances  and  the  formation  of  nitric  acid.  The 
glass  powder  is  moistened  with  water  from  above; 
strong  suction  is  then  applied  at  e  by  attaching  an 
aspirator  thereto,  and  the  excess  of  water  which  is 
thus  drawn  off  from  the  powdered  glass  is  removed 
at  c.  2  ccm.  of  dilute  blood  (1 :  40)  is  then  allowed 
to  drop  from  above,  from  a  pipette,  upon  the  moist- 
ened glass,  a  is  closed,  and  by  gently  blowing  into 
h  with  the  mouth  a  uniform  distribution  of  the 
blood  solution  throughout  the  column  of  powdered 
glass  down  to  the  glass-wool  is  effected.  The  ap- 
paratus is  ready  for  the  absorption,  and  it  is  now 
connected  either  at  e  with  the  aspirator  or  at  h 
with  the  bottle,  depending  upon  whether  the  10  liters 
of  air  are  to  be  drawn  through  or  driven  through. 
An  ordinary  bottle  containing  somewhat  more  than 
10  liters  is  very  well  suited  to  the  taking  of  the 
sample  of  the  air  to  be  examined.  This  bottle  is 
supplied  with  a  double-bore  rubber  stopper,  through 
the  openings  of  which  pass  two  glass  tubes  bent  at 


220  GAS   ANALYSIS  PART  n 

right  angles  above  the  stopper.  One  of  these  tubes 
ends  just  below  the  stopper,  and  the  other  reaches  to 
the  bottom  of  the  bottle.  Pieces  of  rubber  tubing 
of  sufficient  length,  and  closed  by  Bunsen  screw- 
pinchcocks,  are  slipped  over  the  free  ends  of  both 
tubes.  Since  the  bottle  holds  more  than  10  liters  i4: 
is  provided  near  the  bottom  with  a  mark,  from 
which  point  up  to  the  stopper  the  capacity  is  exactly 
10  liters.  To  fill  the  bottle  with  the  air  to  be  exam- 
ined, it  is  filled  completely  with  water,  and  this  is 
then  run  out  through  the  rubber  tube  which  is  con- 
nected to  the  longer  glass  tube,  and  which  acts  as  a 
siphon.  When  the  water  has  fallen  to  the  10  liters 
mark  both  pinchcocks  are  closed.  To  pass  the  air 
through  the  absorption  apparatus,  the  same  rubber 
tube  which  has  acted  as  a  siphon  is  attached  to  a 
bottle  filled  with  water,  and  standing  higher  than  the 
first  bottle,  and  the  other  rubber  tube  is  connected 
with  the  absorption  apparatus.  The  current  of  air, 
which  may  be  very  exactly  regulated  by  means  of 
the  screw-pinchcock,  must  pass  through  the  absorp- 
tion apparatus  very  slowly — on  an  average,  1000  ccm. 
in  twenty  to  twenty-five  minutes.  To  be  able  to 
observe  and  regulate  the  passage  of  the  air  through 
the  apparatus,  2  to  3  ccm.  of  water  are  run  in  at  b 
after  the  powdered  glass  has  been  moistened  with  the 
blood  solution.  When  the  experiment  is  ended,  this 
water  is  let  out  at  c.  Any  burette  holder  is  suited 
to  holding  the  absorption  apparatus ;  a  Vogel  *  uni- 
versal stand '  is  also  well  adapted  to  the  purpose. 
If  it  be  desired  to  draw  the  air  of  the  room  in  ques- 
tion directly  through  the  apparatus,  —  a  proceeding 
which  is,  however,  not  to  be  recommended  because 


CHAP,  iv    DETERMINATION   OF   CARBON  MONOXIDE    221 

of  the  possible  change  in  the  composition  of  the  air 
during  the  long  duration  of  the  experiment,  —  the 
end  h  is  joined  by  a  cork  to  a  so-called  calcium  chlor- 
ide cylinder  containing  pieces  of  pumice-stone  moist- 
ened with  water.  The  air  enters  the  cylinder  from 
below,  becomes  saturated  with  moisture,  and  then 
passes  into  the  absorption  apparatus.  When  10  liters 
of  air  have  been  led  through,  in  one  manner  or  the 
other,  the  stopper  at  c  is  removed  to  let  out  the  water. 
A  small  test-tube,  upon  which  is  a  mark  for  3ccm., 
is  then  placed  under  c,  the  stopper  at  a  is  removed, 
and  pure  water  is  slowly  dropped  from  a  pipette 
upon  the  powdered  glass.  The  blood  solution  is 
thus  gradually  displaced,  and  the  washing  is  con- 
tinued in  this  manner  until  the  liquid  in  the  test- 
tube  amounts  to  3  ccm.  The  tube  is  then  taken 
away,  several  cubic  centimeters  of  water  are  allowed 
to  flow  through  the  powdered  glass,  all  the  stoppers 
are  inserted,  e  is  connected  with  the  aspirator,  and 
when  the  excess  of  water  has  thus  been  removed  the 
apparatus  is  ready  for  another  experiment. 

"  The  same  powdered  glass  was  used  for  from  50 
to  60  determinations  without  it  being  necessary  to 
renew  it.  The  absorption  apparatus  contained  origi- 
nally 2  ccm.  of  dilute  blood  1 :  40 ;  hence  the  3  ccm. 
now  in  the  test-tube  have  a  concentration  of  1 :  60. 

"Small  rectangular  bottles,  with  flat  sides  which 
are  0.5  cm.  and  1  cm.  wide,  are  very  well  suited  to 
holding  the  blood  solution  for  the  observations  with 
the  spectroscope  :  these  little  bottles  hold  about  1.5 
ccm.  of  solution,  and  are  closed  with  carefully  ground 
stoppers.  One  of  these  bottles  is  filled  with  the  blood 
solution  used  in  the  experiment,  and  a  second  bottle 


222  GAS   ANALYSIS  PART  n 

is  filled  with  the  original  blood  solution,  also  diluted 
to  1 :  60.  One  drop  of  ammonium  sulphide  is  added 
to  the  contents  of  each  bottle ;  the  bottles  are  shaken, 
and  after  half  an  hour  the  spectra  of  the  two  solu- 
tions are  examined,  preferably  by  lamplight,  with  a 
delicate  pocket  spectroscope. 

"  When  the  method  is  carried  out  as  just  described, 
it  admits  of  a  comparison  of  the  two  blood  solutions 
under  quite  similar  and  at  the  same  time  the  most 
favourable  conditions  as  regards  the  concentration, 
the  thickness  of  the  observed  column  of  liquid,  the 
reducing  agent,  and  the  duration  of  the  experiment. 
With  respect  to  the  lowest  limit  of  the  possible  and 
certain  detection  of  carbon  monoxide  in  atmospheric 
air,  I  have,  after  many  experiments,  come  to  the  same 
result  as  Hempel,  viz.,  0.03  per  cent.  At  this  con- 
centration both  bands  are  still  distinctly  recognisable. 
When  the  air  contains  less  carbon  monoxide,  about 
0.02  per  cent,  the  presence  of  the  gas  is  shown  merely 
by  a  somewhat  stronger  absorption  in  the  absorption 
spectrum,  which  now  appears  at  D  as  a  broad  band, 
the  maximum  absorption  of  the  reduced  blood  solu- 
tion lying  toward  E.  This  observation  is  the  last 
evidence,  as  Jaderholm  has  already  stated  in  his 
admirable  paper  upon  the  lego-medical  diagnosis  of 
carbon  monoxide  poisoning,  p.  22,  which  shows  that 
some  carbon  monoxide  is  still  present. 

"  It  is  very  desirable  to  possess  for  these  experi- 
ments a  solution  of  blood  which  is  clear,  and  which 
will  keep  for  a  long  time,  and  the  method  proposed 
by  Jaderholm  (p.  30  of  his  article)  answers  the  pur- 
pose excellently.  He  mixes  together  equal  volumes 
of  blood  freed  from  fibriue,  and  of  cold  saturated 


CHAP,  iv    DETERMINATION   OF   CARBON   MONOXIDE    223 

borax  solution.  The  addition  of  the  borax  prevents 
putrefaction  and  does  not  change  the  spectroscopic 
properties  of  the  blood,  and  reduction  and  combina- 
tion with  oxygen  or  carbon  monoxide  take  place  in 
the  same  manner  as  in  fresh  blood  or  haemoglobin 
solution.  The  haemoglobin  gradually  dissolves  in 
the  liquid,  and,  beginning  at  the  bottom  and  pro- 
ceeding upward,  the  solution  takes  on  a  deep  dark 
red  colour.  Such  a  solution  of  the  colouring  matter 
of  blood  in  borax  remains  clear  for  months,  and  does 
not  need  to  be  filtered  before  being  used  for  the 
spectroscopic  examination.  I  have  used  this  solution 
exclusively  for  my  experiments,  the  desired  concen- 
tration of  1 :  40  being  obtained  by  mixing  1  ccm.  of 
the  solution  with  19  ccm.  of  water.  Even  in  this 
dilution,  the  solution  will  keep  for  several  days. 

"  The  permanence  of  the  carbon  monoxide  reaction 
in  this  dilution,  when  the  solution  is  kept  in  the  small 
and  tightly  closed  absorption  bottles,  is  quite  remark- 
able. I  have  kept  solutions  with  0.03  per  cent  and 
0.05  per  cent,  together  with  the  comparing  solutions, 
for  over  three  months  without  the  reaction  becoming 
less  distinct. 

"  I  will  mention  one  other  experiment  which  is  of 
interest  as  serving  to  call  attention  to  certain  neces- 
sary precautions  in  the  examination  of  the  air  of  rooms 
filled  with  coal-gas. 

"  After  the  delicacy  of  the  method  had  been  proved 
by  many  experiments,  it  remained  to  test  it  also  in 
a  practical  manner.  For  this  purpose  a  small  stove 
filled  with  burning  charcoal  was  placed  in  a  closed 
room  in  my  laboratory,  and  the  doors  and  openings 
into  the  chimney  were  closed.  Into  the  room  was 


224  GAS  ANALYSIS  PART  n 

passed  a  glass  tube  with  a  funnel-shaped  mouth. 
This  tube  was  connected  with  a  Mitscherlich  bulb 
apparatus  filled  with  water  for  washing  the  gas,  and 
this  was  joined  to  a  10-liter  bottle  which  aspirated 
the  air.  At  the  same  time  a  100-ccm.  bottle,  filled 
with  water,  was  emptied  in  the  same  room,  3  ccm.  of 
very  dilute  blood  was  put  into  it,  and  the  walls  of  the 
bottle  were  rinsed  for  three  to  four  minutes  with  this 
solution.  Both  experiments  were  begun  after  the 
charcoal  had  burned  in  the  small  room  for  about  half 
an  hour,  at  which  time  the  air  was  stifling  and  of  a 
peculiar  acid  odour,  while  what  is  commonly  termed 
coal-gas  was  present  in  large  amounts.  Nevertheless 
the  Vogel  test  showed  no  trace  of  carbon  monoxide, 
and,  moreover,  my  method,  which  had  shown  itself 
at  other  times  to  be  so  delicate,  failed  me  completely, 
because  all  the  colouring  matter  of  the  blood  in  the 
powdered  glass  was  destroyed  in  a  short  time  and 
the  solution  was  consequently  decoloured.  It  was 
evident,  as  was  already  shown  by  the  slight  bluish 
appearance  in  the  bottle,  that  in  spite  of  the  inter- 
posed wash-bottle  there  had  passed  over  those  acid 
products  of  the  decomposition  and  dry  distillation 
of  coal  (perhaps  phenol),  which  form  when  the  coal 
is  not  completely  burned,  and  which  Hiinefeld,  in 
his  work  upon  the  legal  tests  for  blood  and  carbon 
monoxide  in  blood,1  has  described  in  detail  and  has 
attempted  to  isolate. 

"  The  bottle  containing  the  remainder  of  the  gas 
and  some  water  was  shaken  several  times  and  was 
allowed  to  stand  until  the  next  day  ;  these  substances 
were  then  absorbed,  and  5  liters  of  the  air  still  remain- 

1  Leipsic,  1875,  p.  40. 


CHAP,  iv     DETERMINATION  OF   CARBON   MONOXIDE    225 

ing  in  the  bottle  sufficed  to  give  undoubted  evidence 
of  the  presence  of  carbon  monoxide.  It  would,  how- 
ever, be  advisable  to  interpose  a  cylinder  filled  with 
coarse  and  moist  powdered  glass,  and  another  filled 
with  freshly  slaked  lime,  as  Wolff hugel  has  recom- 
mended." 


FIG.  81. 

S.  Kostin  has  found1  that  it  is  possible  to  detect 
one  part  of  carbon  monoxide  in  40,000  parts  of  air. 
He  first  removes  the  oxygen  of  the  air  by  passing 
the  latter  through  3  liters  of  a  saturated  solution  of 
ferrous  sulphate  to  which  1  liter  of  strong  ammonium 
hydroxide  has  been  added.  The  solution  is  placed  in 
an  aspirator  bottle  that  is  filled  with  iron  gauze  (see 
A,  Fig.  81).  4  liters  of  this  solution,  which  contains 

lArchiv  fur  die  Gesammte  Physiologic,  83  (1901),  572. 
Q 


226  GAS  ANALYSIS  PART  n 

much  undissolved  ferrous  hydroxide,  is  able  to  ab- 
sorb the  oxygen  in  from  80  to  100  liters  of  air.  The 
volume  of  air  under  examination  is  passed  from  one 
such  aspirator  into  another  through  an  interposed 
blood  solution  contained  in  K,  until  all  oxygen  has 
been  removed.  To  prevent  ammonia  vapor  from 
coming  into  contact  with  the  blood,  the  air  is  first 
caused  to  pass  through  wash-bottles  B  and  B'  con- 
taining oxalic  acid.  It  takes  about  two  hours  to 
completely  remove  the  oxygen  from  the  volume  of 
air  above  mentioned. 

A  number  of  chemists  have  busied  themselves 
with  the  investigation  of  various  methods  for  detect- 
ing the  presence  of  carbon  monoxide  in  blood.  Of 
all  the  methods  that  have  been  proposed,  Kostin  con- 
siders that  suggested  by  Kunkel  to  be  the  best.  The 
blood  is  here  diluted  with  10  volumes  of  water  and 
an  equal  volume  of  a  3  per  cent  tannin  solution  is 
then  added.  If  the  blood  contains  carbon  monox- 
ide, a  reddish  precipitate  is  formed,  while  with  normal 
blood  the  precipitate  is  dark  brown.  These  colour 
reactions  become  especially  distinct  after  five  or  six 
hours. 

C.  de  la  Harpe  and  Reverdine1  first  used  the  re- 
action between  iodine  pentoxide  and  carbon  monoxide 
for  the  detection  of  the  latter  substance,  the  reaction 
being  I2O5  +  5  CO  =  21  +  5  CO2,  and  Nicloux2  and 
Gautier3  employed  this  reaction  for  the  quantitative 
determination  of  carbon  monoxide.  Kinnicutt  and 
Sanford4  have  shown  that  this  method  can  be  used 
for  the  detection  of  very  small  amounts  of  carbon 

1  Chem.  Ztg.  12  (1888),  1726.  2  Compt.  rend.  126,  746. 

8  Ibid.,  126,  931.  *J.  Am.  Chem.  tioc.  22  (1900),  14. 


CHAP,  iv          DETERMINATION   OF   METHANE  227 

monoxide  not  only  in  air,  but  also  in  illuminating 
gas,  provided  the  latter  is  first  passed  through  two 
U -tubes,  one  containing  sulphuric  acid  and  the  other 
small  pieces  of  potassium  hydroxide.  The  iodine  set 
free  in  the  reaction  is  titrated  with  a  -J^Q  solution  of 
sodium  thiosulphate.  By  this  method  it  is  possible 
to  detect  one  part  of  carbon  monoxide  in  40,000  parts 
of  air  when  using  as  small  a  volume  of  air  as  1  liter. 
Carbon  monoxide  may  also  be  detected  with 
sodium  palladium  chloride,  metallic  palladium  being 
thrown  down  and  the  gas  being  changed  to  carbon 
dioxide.  But  palladium  chloride  is  also  decomposed 
by  a  large  number  of  organic  substances,  and  mis- 
takes may  arise  from  this  cause. 

METHANE  (CH4) 
Marsh-gas  —  Fire-damp 

Specific  gravity,  0.55297;  weight  of  1  liter,  0.71549; 
critical  temperature,  —82°;  critical  pressure,  55  at- 
mospheres ;  boiling-point  at  a  pressure  of  one  atmos- 
phere, —  152.5°;  freezing-point,  —185.8°;  specific 
gravity  of  liquid  methane,  0.415. 

According  to  Bunsen,  1  volume  of  water  absorbs 
at  a  temperature  £, 

0.05449-0.0011807*  +  0.000010278 1* ; 
hence  at  20°,  0.0349812  volume. 

One  volume  alcohol  absorbs  at  temperature  £, 

0.522586  -  0.0028655 1  +  0.0000142  £2 ; 
hence  at  20°,  0.47096  volume. 

1  vol.  CH4  =  2  vol.  H  +  i  vol.  C. 


228  GAS   ANALYSIS  PART  n 

Marsh-gas  is  always  determined  by  combustion. 
One  volume  of  methane  unites  with  2  volumes  of 
oxygen,  and  1  volume  of  carbon  dioxide  is  formed. 

To  avoid  the  burning  of  nitrogen  in  the  explosion, 
100  volumes  of  incombustible  gas  are  taken  for  from 
25  to  37  volumes  of  the  mixture  of  methane  and 
oxygen  (Bunsen). 

No  absorbent  for  marsh-gas  is  known. 

ETHYLENE  (C2H4) 

Specific  gravity,  0. 96744 ;  weight  of  1  liter,  1 . 25178 ; 
critical  temperature,  -f- 10°  C. ;  critical  pressure,  51 
atmospheres;  boiling-point  at  a  pressure  of  one  at- 
mosphere, —  102.65°;  specific  gravity  of  liquid  ethy- 
lene,  0.6095, 

2  vol.  C2H4  =  4  vol.  H  +  2  vol.  C. 
One  volume  of  water  absorbs  at  temperature  £, 

0.25629  -  0.00913631*  +  0.000188108 *2; 
hence  at      20°,  0.1488  volume  (Bunsen). 
One  volume  of  alcohol  absorbs  at  £°, 

3.59498  -  0.057716*  +  0.0006812*2; 
hence  at      20°,  2.7131  volumes  (Carius). 

Ether  absorbs  about  twice  its  volume,  turpentine 
oil  and  petroleum  two  and  a  half  times  their  volumes, 
and  olive  oil  its  own  volume  of  ethylene. 

Either  fuming  sulphuric  acid  or  bromine  water  is 
used  for  the  absorption. 

It  is  advisable  to  use  sulphuric  acid  so  concen- 


CHAP.  IV 


DETERMINATION   OF  ETHYLENE 


229 


trated  that  when  the  temperature  is  slightly  lowered, 
crystals  will  appear. 

The  analytical  absorbing  power  is  8. 

The  acid  is  used  in  a  simple  pipette  which  has 
three  bulbs  (Fig.  82).  The  small  bulb  is  filled  by 
the  glass-blower  with  glass  beads,  which  serve  to 
give  to  the  sulphuric  acid  the  largest  possible  sur- 
face. With  this  arrangement  the  complete  absorp- 
tion of  the  heavy  hydrocarbons,  and  of  ethylene  in 
particular,  is  effected  by  passing  the  gas  into  the 
pipette  but  once. 

In  this  reaction  some  sulphur  dioxide  is  usually 
formed,  and,  moreover, 
the  vapour  of  fuming 
sulphuric  acid  has  a 
very  high  tension,  so 
that  the  gas  residue, 
before  being  measured, 
must  be  freed  from  the 
acid  vapours  in  the 
caustic  potash  pipette, 
a  single  passage  of  the 
gas  into  the  pipette 
being  also  here  suf- 
ficient. 

To  avoid  having  the 
rubber  connections  be- 
tween the  pipette  and 
burette  attacked  by 
the  fuming  sulphuric 
acid,  the  apparatus  is  so  put  together  that  the  sul- 
phuric acid  does  not  quite  fill  the  capillary  of  the 
pipette,  and  the  connecting  capillary  is  allowed  to 


230  GAS   ANALYSIS  PART  11 

remain  empty ;  the  short  rubber  tube  of  the  burette 
is  also  freed  from  liquid  by  means  of  a  narrow  tipped 
suction  pipette,  any  reagent  remaining  in  the  rubber 
tube  being  first  washed  out  by  water  with  the  same 
pipette.  If  care  be  taken  that  the  sulphuric  acid  is 
stopped,  after  the  absorption,  at  the  same  point  in 
the  capillary  at  which  it  stood  when  the  burette  and 
pipette  were  first  put  together,  then  the  small  volume 
of  air  contained  in  the  empty  capillary  tubes  in  the 
beginning  causes,  of  course,  no  error  in  the  deter- 
mination of  the  heavy  hydrocarbons  or  other  gases, 
with  the  exception  of  nitrogen.  In  the  nitrogen 
determination,  allowance  may  be  made  for  this  air 
volume,  but  as  each  centimeter  of  the  empty  capillary 
corresponds  to  only  0.008  ccm.,  this  value  falls  below 
the  limit  of  the  usual  unavoidable  experimental 
errors. 

After  the  absorption,  the  rubber  tube  is  taken  off 
from  the  pipette,  and  the  capillary  and  the  larger 
tube  are  closed  air-tight  by  little  glass  caps,  which 
are  pushed  over  narrow  rubber  rings  placed  upon 
the  tubes. 

Bromine  is  a  good  absorbent  for  ethylene.  It  is 
used  in  a  pipette  similar  to  the  one  just  described. 
It  is  not  necessary  to  fill  the  pipette  completely  with 
bromine,  it  being  quite  sufficient  if  a  few  cubic  centi- 
meters of  bromine  lie  under  water  in  the  pipette. 
There  is  thus  formed  a  saturated  solution  of  bromine 
in  water,  which  absorbs  the  ethylene.  According  to 
experiments  of  Cl.  Winkler,1  however,  the  absorption 
is  not  a  complete  one,  and  it  is  better  to  use  fuming 
sulphuric  acid  for  this  purpose. 

1  Zeitschriftfur  analyt.  Chemie,  28,  269-289, 


CHAP,  iv        DETERMINATION   OF   ACETYLENE  231 

ACETYLENE  (C2H2) 

Specific  gravity,  0.89820;  weight  of  1  liter,  1.16219; 
critical  temperature,  36.9°;  critical  pressure,  67.96 
atmospheres ;  specific  gravity  of  liquid  acetylene  at 
0°  =  0.45. 

2  vol.  C2H2  =  2  vol.  H  +  2  vol.  C. 

Acetylene  is  somewhat  soluble  in  water,1  which  dis- 
solves its  equal  volume  of  the  gas.  Oil  of  turpentine 
and  tetra-chlor-methane  dissolve  2  volumes  of  the  gas, 
amyl  alcohol  and  styrol  3^,  chloroform  and  benzol  4, 
glacial  acetic  acid  and  alcohol  6.  It  is  slowly  absorbed 
by  concentrated  sulphuric  acid,  acetyl  sulphonic  acid 
being  formed.  An  ammoniacal  solution  of  cuprous 
chloride  absorbs  the  gas  rapidly  and  there  is  formed 
a  brown  to  violet-red  precipitate  of  copper-acetylene, 
which  explodes  when  heated  or  struck.  Acetylene 
produces  in  an  ammoniacal  silver  solution  a  white 
precipitate  similar  to  the  last,  but  even  more  explosive 
than  the  copper-acetylene.  If  the  gas  is  led  into 
ammoniacal  solutions  of  aurous  thiosulphate,  or  po- 
tassium mercuric  iodide,  exceptionally  explosive  com- 
pounds are  formed. 

All  of  the  ammoniacal  solutions  of  metals  which 
have  been  mentioned  may  be  used  as  absorbents  for 
acetylene. 

Although  acetylene  can  be  determined  by  combus- 
tion with  oxygen,  this  method  cannot  usually  be 
employed,  because  the  gas  occurs  in  mixtures  with 
other  combustible  gases.  One  volume  of  acetylene 

1  The  following  details  are  taken  from  Winkler's  Anleitung  zui 
chemischen  Untersuchung  der  Industrie- Gase,  Part  I,  p.  100. 


232  GAS  ANALYSIS  PART  n 

yields  on  combustion  2  volumes  of  carbon  dioxide. 
When  2  volumes  of  acetylene  are  burned  there  is 
a  contraction  of  3  volumes. 

2  C2H2  +  5  02=  2  H20  +  4  CO2. 

liquid 

It  is  best  determined  by  leading  it  through  an  am- 
moniacal  cuprous  chloride  solution,  a  reddish  brown 
precipitate  being  thrown  down.  The  precipitate  is 
filtered  off,  and  is  washed  with  water  containing  am- 
monia until  the  wash- water  passes  through  colourless. 

Since  copper-acetylene  explodes  at  95°,  the  acety- 
lene is  calculated  from  the  copper  oxide  in  the  precipi- 
tate. The  copper-acetylene  has  the  composition  l 

C2Cur 

To  determine  the  amount  of  copper  present,  hydro- 
chloric acid  is  poured  over  the  copper-acetylene,  de- 
composing it  with  evolution  of  acetylene.  As  it  is 
difficult  to  completely  decompose  the  copper-acety- 
lene, the  end  of  the  reaction  is  not  waited  for,  but 
the  rest  of  the  precipitate,  without  being  washed,  is 
dried  on  the  filter  and  ignited.  The  copper  oxide  is 
dissolved  in  a  few  drops  of  nitric  acid,  and  this  solu- 
tion is  added  to  the  hydrochloric  acid  filtrate  first 
obtained.  The  solution  is  then  precipitated  hot  with 
sodium  hydroxide,  and  the  copper  oxide  is  filtered  off, 
ignited,  and  weighed. 

The  ignition  temperature  of  acetylene  when  mixed 
with  any  more  than  35  per  cent  of  air  is  480°  C. 
The  temperature  of  dissociation  of  acetylene  is  780°  C. 

1  Reiser,  American  Chemical  Journal,  1892,  p.  285. 


CHAP,  iv  DETERMINATION  OF   CYANOGEN  233 

CYANOGEN  (C2N2) 

Specific  gravity,  1.79907;  weight  of  1  liter, 
2.32784. 

2  vol.  C2N2  =  2  vol.  C  +  2  vol.  N. 

One  volume  of  water  dissolves  at  20°,  4.5  volumes 
of  cyanogen  ;  1  volume  of  alcohol,  20  volumes  of 
cyanogen. 

Burned  with  twice  its  volume  of  oxygen  it  forms 
2  volumes  of  carbon  dioxide  and  1  volume  of  nitrogen. 

Cyanogen  gas  is  soluble  in  benzene. 

Free  cyanogen,  or  dicyanogen,  may  be  detected 
according  to  Kunz-Krause 1  by  the  Schonbein-Pagen- 
stecher  reaction.  For  carrying  out  this  test,  strips 
of  filter  paper  are  first  dipped  into  a  dilute  aqueous 
solution  of  copper  sulphate  (1:1000),  and  are  then 
impregnated  with  a  3  per  cent  tincture  of  gum  guaiac. 
The  paper  thus  prepared  turns  blue  when  acted  upon 
by  dicyanogen  or  hydrocyanic  acid,  but  this  blue 
colour  is  also  caused  by  certain  oxidising  agents  such 
as  ozone  and  nitric  acid. 

The  reaction  is  somewhat  sharper  when  the  gas 
mixture,  instead  of  being  brought  in  contact  with 
the  paper  above  described,  is  passed  through  a  wash- 
bottle  containing  an  alcoholic  copper  sulphate  —  gum 
guaiac  solution. 

The  reaction  has  lately  been  increased  in  delicacy 
by  E.  Schaer,  who  uses  guaiaconic  acid  in  place  of 
the  gum  guaiac.  The  reagent  should  always  be 
freshly  prepared,  and  this  is  done  by  adding  to 
10  ccm.  of  a  dilute  aqueous  copper  sulphate  solution 

1  Zeitschr.  angew.  Chem.,  26  (1901),  652. 


234  GAS   ANALYSIS  PART  n 

15  com.  of  alcohol  in  which  a  little  guaiaconic  acid 
has  previously  been  dissolved. 

Another  delicate  reaction  for  dicyanogen  is  given 
by  Kunz-Krause  in  the  article  above  cited,  this  test 
depending  upon  the  formation  of  isopurpuric  acid  or 
picrocyaminic  acid,  C8H5N5O6,  from  picric  acid. 
2  com.  of  a  cold  saturated  aqueous  solution  of  picric 
acid  (1.86)  is  mixed  with  18  ccm.  of  alcohol  and 
5  ccm.  of  a  15  per  cent  aqueous  solution  of  potassium 
hydroxide.  When  brought  into  contact  with  this 
solution  pure  cyanogen  yields  a  deep  purple  red 
colour,  which  later  turns  to  brown.  On  long  stand- 
ing the  potassium  salt  of  isopurpuric  acid  separates 
in  the  form  of  an  oil  of  purple  red  colour.  This  re- 
agent also  must  always  be  freshly  prepared. 

Caustic  potash  absorbs  cyanogen,  potassium  cya- 
nide and  potassium  cyanate  being  formed, 

C2N2  +  2  KOH  =  KCN  +  KCNO  +  H2O. 

Cyanogen  is  determined  by  absorbing  it  in  a  solu- 
tion of  potassium  hydroxide,  adding  silver  nitrate, 
and  then  slightly  acidifying  with  nitric  acid.  The 
precipitate  is  filtered  off,  converted  into  metallic 
silver  by  ignition  in  a  porcelain  crucible,  and  is  then 
weighed. 

HYDROCYANIC  ACID  (HCN) 

Specific  gravity,  0.9359;  weight  of  1  liter,  1.2096. 

The  gas  is  easily  soluble  in  water  and  in  alcohol. 
Potassium  hydroxide  absorbs  it,  potassium  cyanide 
being  formed. 

Strong  acids,  especially  hydrochloric  acid  and  sul- 


CHAP,  iv     DETERMINATION  OF  HYDROCYANIC  ACID    235 

phuric  acid,  decompose  hydrocyanic  acid  with  forma- 
tion of  formic  acid  and  ammonia. 

To  detect  the  acid,1  add  ferrous  sulphate  and  one 
drop  of  ferric  chloride  to  the  solution  of  hydrocyanic 
acid  or  potassium  cyanide,  then  add  potassium  hy- 
droxide to  alkaline  reaction  if  the  solution  is  not 
already  alkaline,  warm  gently,  and  acidify  with 
hydrochloric  acid.  A  dark  blue  precipitate  of  Prus- 
sian blue  results. 

Another  test  for  hydrocj^anic  acid  is  to  add  ammo- 
nium sulphide  until  the  solution  takes  on  a  yellow 
colour,  then  ammonia,  —  or,  better,  a  drop  of  so'dium 
hydroxide,  —  and  to  heat  the  solution  until  the  excess 
of  ammonium  sulphide  has  been  driven  off,  and  the 
solution  is  again  colourless.  In  this  way  there  is 
formed  either  ammonium  or  sodium  sulphocyanate, 
which,  after  acidifying,  gives  the  characteristic  blood- 
red  colour  with  ferric  chloride. 

Hydrocyanic  acid  is  determined  by  absorbing  it 
with  a  solution  of  potassium  hydroxide,  and  precipi- 
tating it  with  silver  nitrate,  exactly  as  given  for 
cyanogen. 

The  reactions  are  as  follows :  — 

HCN  +  KOH     =KCN    +H2O 

KCN  +  AgNO3  =  AgCN  +  KNO3 

HYDROGEN  SULPHIDE  (H2S) 

Specific  gravity,  1.17697 ;  weight  of  1  liter, 
1.52290;  boiling-point,  81.8°;  melting-point,  -85°. 

2  vol.  H2S  =  2  vol.  H  +  1  vol.  S. 

1  Cl.  Winkler,  Anleitung  zur  chemischen  Untersuchung  der  In- 
dustrie- Gase,  Part  I,  p.  60. 


236  GAS   ANALYSIS  PART  n 

According  to  Bunsen's  experiments,  water  absorbs  — 

At    2°     C.,  4.2373  vol.  H2S 

«     9.8°  C.,  3.5446    "    H2S 

"  14.6°  C.,  3.2651     «    H2S 

"  19°     C.,  2.9050    «    H2S. 

Between  2°  and  43.3°  the  absorption  by  1  volume 
water  at  t° 

=  4. 3T06  -  0.083687 1  +  0. 0005213  £2  volumes  of  H2S. 

According  to  the  same  authority  alcohol  takes  up, 
between  1°  and  22°,  at  temperature  t, 

17.891  -0.65598 £  +  0. 00661  $  volumes. 

One  and  a  half  volumes  of  oxygen  are  necessary 
for  the  combustion  of  1  volume  of  hydrogen  sul- 
phide, and  1  volume  of  sulphur  dioxide  is  formed. 

When  sulphur  trioxide  is  brought  into  contact 
with  hydrogen  sulphide,  sulphuric  acid,  sulphur 
dioxide,  and  sulphur  result  — 

2  S03  4-  H2S  =  H2S04  +  S02  +  S. 

Potassium  hydroxide  and  solutions  of  many  of  the 
heavier  metals  absorb  hydrogen  sulphide,  and  give 
the  corresponding  compound.1 

If  hydrogen  sulphide  is  present  in  any  consider- 
able amount,  its  presence  is  shown  by  its  odour.  A 
surer  test  is  to  introduce  into  the  gas  a  strip  of  so- 
called  lead-paper.  The  paper  becomes  covered  with 
a  glistening  brownish  black  layer  of  lead  sulphide, 
even  when  only  traces  of  hydrogen  sulphide  are 
present. 

1  Cl.  Winkler,  Arileitung  zur  Untersuchung  der  Industrie- Gase, 
Part  I,  p.  60. 


CHAP,  iv  HYDROGEN   SULPHIDE  237 

Concentrated  nitric  acid  and  solutions  of  chromic 
acid,  permanganic  acid,  ferric  oxide,  chlorine,  bro- 
mine, iodine,  and  of  the  oxygen  acids  of  the  last 
three,  decompose  hydrogen  sulphide  immediately, 
with  the  separation  of  free  sulphur  ;  in  the  presence 
of  an  excess  of  the  halogens,  the  sulphur  is  finally 
attacked  and  wholly  or  partly  converted  into  sul- 
phuric acid. 

Hydrogen  sulphide  may  be  quantitatively  deter- 
mined by  Dupasquier's  method,  a  measured  quantity 
of  gas  (see  Fig.  62)'  being  drawn  through  a  solution 
of  iodine  in  potassium  iodide,  to  which  some  starch 
paste  has  been  added.  The  operation  is  stopped  as 
soon  as  the  solution  becomes  colourless.  The  re- 
action is  — 


but  the  reaction  follows  this  equation  precisely  only 
when  the  solutions  are  very  dilute  and  protected 
from  direct  sunlight. 

R.  Fresenius  l  determines  hydrogen  sulphide  gravi- 
metrically  by  first  drying  the  gases  with  calcium 
chloride  and  then  absorbing  the  hydrogen  sulphide 
in  U  -tubes  which  are  filled  |  with  pumice-stone 
impregnated  with  copper  sulphate,  and  J,  at  the  exit 
end,  with  calcium  chloride.  The  pumice-stone  is 
prepared  as  follows  :  Place  60  g.  of  pumice-stone, 
in  pieces  the  size  of  a  pea,  in  a  small  porcelain 
dish,  and  pour  a  hot  concentrated  solution  of  from 
30  to  35  g.  of  copper  sulphate  over  it.  Evaporate 
the  solution  to  dryness  with  constant  stirring,  place 

1  R.  Fresenius,  Anleitung  zur  quant.  Analyse,  6th  ed.,  Part  I, 
p.  505.  Also  Zeitschr.  f.  analyt.  CJiemie,  10,  75. 


238  GAS   ANALYSIS  PART  n 

the  dish  in  an  air-  or  oil-bath,  whose  temperature 
is  kept  between  150°  and  160°  C.,  and  let  it  remain 
there  four  hours. 

A  tube  containing  14  g.  of  this  copper  sulphate 
pumice-stone  takes  up  about  2  g.  of  hydrogen  sul- 
phide. To  make  sure  of  complete  absorption  two 
such  tubes  should  always  be  used.  When  the 
pumice-stone  is  less  thoroughly  dried,  it  takes  up 
a  much  smaller  amount  of  hydrogen  sulphide,  and 
when  it  has  been  dried  at  a  higher  heat  —  until  it 
has  lost  its  water  of  crystallisation  —  it  causes  a 
decomposition  of  the  hydrogen  sulphide  and  the 
evolution  of  sulphur  dioxide. 

Hydrogen  sulphide  can  also  be  determined  by 
passing  the  gas  through  a  solution  of  bromine  in 
water,  precipitating  the  sulphuric  acid  thus  formed 
with  barium  chloride,  and  weighing  as  barium  sul- 
phate. 

According  to  Bunsen1  it  is  possible  to  determine 
the  hydrogen  sulphide  of  a  gas  mixture  containing 
hydrogen,  nitrogen,  carbon  dioxide,  hydrocarbons, 
etc.,  by  means  of  balls  of  manganese  dioxide.  The 
purest  pyrolusite  is  ground  to  a  very  fine  powder, 
and  is  then  stirred  with  sufficient  distilled  water  to 
make  a  thin  paste.  The  balls  are  made  from  this 
paste  by  pressing  it  in  a  bullet-mould  which  has 
been  rubbed  with  oil.  The  balls  are  dried  in  an 
air-bath,  and  are  then  covered  with  a  concentrated 
sirupy  solution  of  phosphoric  acid. 

1  Bunsen,  Grasometrische  Methoden,  2d  ed.,  p.  111. 


CHAP,  iv      DETERMINATION   OF   SULPHUR   DIOXIDE     239 

SULPHUR  DIOXIDE  (SO2) 

Specific  gravity,  2.21295;  weight  of  1  liter,  2.86336; 
melting-point,  —76°  ;  boiling-point,  —8°  ;  specific 
gravity  of  liquid  sulphur  dioxide  at  —20°=  1.49. 

2  vol.  SO2  =  1  vol.  S  +  2  vol.  O. 

Sulphur  dioxide  is  easily  soluble  in  water.  Ac- 
cording to  Sims,  1  volume  of  water  dissolves  at 
760  mm.  pressure  — 

At  7°,  61.65  vol.  SO2 
"  20°,  36.43  "  SO2 
«  39.8°,  20.5  "  SO2 
"  50°,  15.62  «  SO2. 

One  volume  of  water  absorbs  at  76  cm.  pressure, 
and  at  temperatures  between  0°  and  20°,  at  £°, 

79.789  -  2.6077*  +  0.029349 1* 

volumes  of  sulphur  dioxide  ;  hence,  1  volume  of  the 
saturated  aqueous  solution  contains,  at  t°, 

68.861  - 1.87025 1  +  0.01225 1* 

volumes  of  the  gaseous  acid. 

For  temperatures  between  21°  and  40°,  the  co- 
efficient of  absorption  is  — 

75.182  -  2.1716  *  +  0.01903 1\ 

and  the  amount  of  gas  contained  by  the  saturated 
aqueous  solution  is  — 

60.952  -  1.38898 1  +  0.00726 12  volumes. 

In  the  solution  which  has  been  saturated  at  0°, 
a  hydrate  separates  out  in  crystals.  These  crystals 


240  GAS   ANALYSIS 


PART  II 


melt  between  1°  and  2°  with  evolution  of  gas,  and 
probably  have  the  formula  — 

H2SO3  + 14  H2O. 

The  solution  of  the  gas  has  a  strong  acid  reaction, 
and  reddens  blue  litmus  paper.  This  the  completely 
dry  gas  does  not  do,  because  sulphurous  acid,  H2SO3, 
is  formed  only  when  the  gas  unites  with  water. 

The  gas  is  condensed  by  pressure  or  cold  to  a 
colourless  mobile  liquid  which  boils  at  —  8°. 

One  volume  of  alcohol  absorbs  at  760  mm.  press- 
ure and  *°,  328.62-  16.95  *  +  0.3119  £2  volumes  of 
sulphur  dioxide.  The  specific  gravity  of  the  solution 
is  then  — 

1.11937  -  0.014091 1+  0.000257  £2  (Carius). 

The  alcoholic  solution  of  sulphur  dioxide,  satu- 
rated at  0°,  contains  216.4  volumes  of  the  gas. 

Alkalies  absorbed  the  gas  very  actively,  with  evo- 
lution of  heat. 

Sulphur  dioxide  is  determined  either  by  leading  a 
measured  volume  of  the  gas  through  a  solution  of 
bromine  in  water,  and  precipitating  the  sulphuric 
acid  thus  formed  by  barium  chloride,  or  by  meas- 
uring the  amount  of  gas  required  to  decolourise  an 
iodine  solution  of  known  strength. 

In  the  latter  method  the  reaction,  when  it  takes 
place  in  aqueous  solutions,  follows  this  equation, 

S02  + 12  +  2  H20  =  H2S04  +  2  HI, 

so  long  as  the  liquid  does  not  contain  more  than  0.04 
per  cent  of  sulphur  dioxide  (Bunsen). 


CHAP,  iv  CAKBON  OXYSULPHIDE  241 

Reich  has  applied  this  method  to  the  determining 
of  sulphur  dioxide  in  the  gases  from  roasting  fur- 
naces (see  p.  323). 

1  ccm.  -~Q  iodine  solution  =  0.0032  g. 


=  0.11  ccm.  SO2. 


CARBON  OXYSULPHIDE  (COS) 

Specific  gravity,  2.07483;  weight  of  1  liter,  2.68464. 

Experimentation  with  carbon  oxysulphide  is  espe- 
cially difficult  because  the  gas  is  easily  decomposed 
by  contact  with  water,  alkalies,  and  acids,  especially 
in  the  light. 

Pure  carbon  oxysulphide  has  a  very  slight  odour 
and  is  very  poisonous. 

The  critical  temperature  is  105°  C. ;  critical  press- 
ure, 63  kg.  per  square  centimeter;  boiling-point  at 
atmospheric  pressure,  —  47.5°  C.  The  pressure 
of  the  gas  at  17.4°  C.  is  8  kg.  per  square  centi- 
meter. 1  ccm.  of  water  at  13.5°  and  756  mm 
pressure  absorbs  0.8  ccm.  of  carbon  oxysulphide. 
The  analytical  absorbing  power  of  a  solution,  pre- 
pared by  dissolving  one  part  of  potassium  hydrox- 
ide in  two  parts  of  water  and  adding  an  equal 
volume  of  alcohol,  is  18  ;  that  is,  a  cubic  centimeter 
of  this  reagent  is  able  to  absorb  72  ccm.  of  carbon 
oxysulphide.  The  gas  is  but  slightly  soluble  in  a 
hydrochloric  acid  solution  of  cuprous  chloride. 
1  ccm.  of  this  solution  absorbs  about  0.2  ccm.  of  the 


2  vol.  COS  =  1  vol.  C  +  1  vol.  O  +  1  vol.  S. 

B 


242  GAS   ANALYSIS  PART  n 

Water  absorbs  about  its  own  volume  of  the  gas, 
and  takes  on  its  odour  and  sweet,  sharp  taste.  The 
gas  is  probably  present  in  many  sulphur  springs. 

One  volume  of  carbon  oxysulphide  needs  1|  volumes 
of  oxygen  for  its  combustion,  and  yields  1  volume  of 
CO2  and  1  volume  of  SO2.  The  mixture  explodes 
with  a  loud  sound  and  a  brilliant  white  flame.  With 
7-|  volumes  of  air  it  burns  quietly.1 

In  a  mixture  of  air  and  carbon  oxysulphide,  the 
latter  can  be  quantitatively  determined  by  combus- 
tion even  when  the  work  is  carried  on  over  aqueous 
solutions.  The  total  contraction  resulting  from  the 
combustion  of  the  gas  and  the  subsequent  absorption 
by  potassium  hydroxide  of  the  sulphur  dioxide  and 
carbon  dioxide  that  are  formed  is  measured,  and 
2J  times  this  contraction  gives  the  volume  of  carbon 
oxysulphide  which  was  present. 

When  mixed  with  hydrogen  sulphide  and  carbon 
dioxide,  carbon  oxysulphide  may  be  determined  by 
first  absorbing  the  hydrogen  sulphide  with  an  acid 
solution  of  copper  sulphate  (see  table  below),  then 
decomposing  the  carbon  oxysulphide  by  heat  into 
carbon  monoxide  and  sulphur,  absorbing  the  car- 
bon monoxide  with  a  hydrochloric  acid  solution  of 
cuprous  chloride,  and  finally  determining  the  carbon 
dioxide  which  may  be  present  by  means  of  potassium 
hydroxide. 

The  heating  of  the  carbon  oxysulphide  is  carried 
on  in  a  platinum  capillary.  Care  must  be  exercised 
to  see  that  the  ends  of  the  capillary  are  not  stopped 
up  by  solidifying  sulphur.  If  this  should  occur,  the 

1  Cl.  Wiakler,  Anleitung  zur  Uutcrsuchung  der  Industrie- Gfase, 
Part  I,  p.  111. 


CHAP,  iv  CAKBON  OXYSULPHIDE  243 

sulphur  can  be  melted  by  heating  the  capillary  up  to 
120°.  The  volume  of  the  carbon  monoxide  which  is 
found  corresponds  exactly  to  that  of  the  carbon  oxy- 
sulphide.  Inasmuch  as  carbon  oxysulphide  is  not 
absorbed  by  a  hydrochloric  acid  solution  of  cuprous 
chloride,  it  can  be  separated  from  carbon  monoxide 
by  means  of  this  reagent. 

The  great  solubility  of  all  of  the  gases  present  in 
such  a  mixture  as  that  described  just  above,  and  the 
instability  of  the  carbon  oxysulphide  itself,  make  it 
impossible  to  obtain  results  of  any  high  degree  of 
accuracy.  An  artificially  prepared  mixture,  con- 
sisting of 

44.3  per  cent,  COS 

37.6        «        H2S 
14.2        "        CO2 
3.9        «         N  +  O  +  H, 

gave  upon  analysis  the  following  results  :  62.2  ccrn. 
of  the  mixture  treated  with  15  ccm.  of  an  acid  copper 
sulphate  solution  showed  an  absorption  of  22.4  ccm.  of 
H2S,  equal  to  36  per  cent  of  that  gas.  The  remainder 
of  the  gas  was  heated  and  a  diminution  in  volume 
amounting  to  39.1  ccm.  resulted.  After  absorption 
with  hydrochloric  acid  cuprous  chloride,  13.5  ccm 
remained,  the  difference,  26.3  ccm.  (  =  42.3  per  cent), 
representing  the  COS  present.  After  absorption 
with  potassium  hydroxide,  5.5  ccm.  of  gas  remained, 
showing  8  ccm.,  or  12  per  cent,  of  CO2  present  in  the 
mixture. 

These  values  show  that  the  results  which  are 
obtained  by  separating  these  gases  by  absorption  are 
only  approximate. 


244 


GAS  ANALYSIS 


PART  n 


Reagent  Employed 

Analytical  Absorbing  Power 

Carbon 
Oxysulphide 

Hydrogen 
Sulphide 

Carbon 
Bisulphide 

Chlorofor™ 

2-3 

1  part  triethyl- 

Mixture  • 

phosphine 

16 

9   parts  chloro- 

form    .     .     . 

Pyridine 

1.1 

4-5 

9 

1  part  triethyl- 

phosphine 

Mixture 

9  parts  pyridine 

3 

26 

26 

* 

10   parts  nitro- 

benzene    .     . 

Nitrobenzene  

3 

2 

46 

1  part  potassium  hydrox- 

ide  in 

2   parts    water. 

One-half  saturated  with 

H2S,  and  the  2  portions 

then  mixed  





1 

Saturated  solution  of  cop- 

per sulphate  in  a  mix- 

ture  of   200   gr.   water 

and  200  gr.  concentrated 

sulphuric  acid  .... 

2.2 

If  carbon  oxysulphide  is  led  through  heated  alka- 
line earths,  alkalies,  or  a  layer  of  red-hot  soda  lime, 
it  is  wholly  absorbed  — 

COS  +  2  CaO  =  CaS  +  CaCO3. 

CHLORINE  (Cl) 

Specific  gravity,  2.44921 ;  weight  of  1  liter,  3.16906; 
critical  temperature,  -f- 141° ;  critical  pressure  83.3 


CHAP,  iv          DETERMINATION   OF   CHLORINE  245 

atmospheres ;  boiling-point  at  a  pressure  of  one 
atmosphere  —  33.6°  ;  specific  gravity  of  liquid  chlor- 
ine =  1.557. 

Chlorine  is  quite  soluble  in  water.  One  part  of 
cold  water  dissolves  approximately  2  volumes  of 
chlorine  ;  hot  water  dissolves  less.  Experiments  by 
Roscoe  have  shown  that  the  absorptions  do  not  fol- 
low the  usual  laws  of  absorption.  According  to 
Schonfeld,  1  volume  of  water  absorbs  the  follow- 
ing volumes  of  chlorine  :  — 

'10°,  2.5852 

15°,  2.3681 

20°,  2.1565 

25°,  1.9504 

30°,  1.7499 

35°,  1.5550 

40°,  1.3656. 

Chlorine  is  best  determined  by  the  Bunsen  pro- 
cedure, in  which  the  gas  is  led  through  a  solution  of 
potassium  iodide,  and  the  iodine  set  free  is  titrated 
with  sodium  thiosulphate  — 

C12  +  2  KI  =  2  KC1  +  I2, 
2  Na2S203  +  I2  =  Na2S406  +  2  Nal. 

Chlorine  can  also  be  absorbed  with  potassium 
hydroxide  or  caustic  soda.  In  cold  dilute  solutions 
potassium  hypochlorite  is  formed  — 

2  KOH  +  C12  =  KC1O  +  KC1  +  H2O. 
In  hot  concentrated  solutions,  the  reaction  is  — 
6  KOH  +  3  C12  =  5  KC1  +  KC1O3  +  3  H2O. 


246  GAS   ANALYSIS  PART  n 

According  to  R.  v.  Wagner,  the  hypochlorite  formed 
may,  after  addition  of  potassium  iodide  and  hydro- 
chloric acid,  be  titrated  with  sodium  thiosulphate. 

If  a  solution  contains  free  chlorine  together  with 
hydrochloric  acid,  they  may  both  be  determined  in 
the  following  manner  (Fresenius) :  — 

To  a  weighed  portion  of  the  liquid  add  an  aqueous 
solution  of  sulphurous  acid  until  the  latter  is  in 
excess;  after  some  time  add  nitric  acid  and  then 
some  potassium  chromate  to  destroy  the  excess  of 
sulphur  dioxide,  and  precipitate  the  total  chlorine  as 
silver  chloride. 

If  now  the  amount  of  free  chlorine  is  determined, 
in  a  second  portion  by  potassium  iodide,  the  differ- 
ence gives  the  quantity  of  chlorine  present  in  the 
form  of  chloride. 

The  total  chlorine  may  also  be  volumetrically 
determined  by  absorbing  the  gases  with  a  solution 
of  sodium  hydroxide,  adding  sulphur  dioxide,  then, 
after  a  while,  nitric  acid  and  some  potassium  chrom- 
ate, and  finally  neutralising  the  solution  by  adding 
calcium  carbonate.  All  chlorine  is  now  present  as 
chloride,  and  the  solution  is  neutral,  so  that  the  chlor- 
ine may  be  titrated  with  a  neutral  silver  solution, 
potassium  chromate  being  used  as  indicator. 


HYDROCHLORIC  ACID  (HC1) 

Specific  gravity,  1.25922;  weight  of  1  liter,  1.62932; 
boiling-point,  —80.3°;  melting-point,  —112.5°;  speci- 
fic gravity  of  liquid  hydrochloric  acid,  1.27. 

2  vol.  HC1  =  1  vol.  Cl  +  1  vol.  H. 


CHAP,  iv  HYDROCHLORIC   ACID  247 

Hydrochloric  acid  dissolves  very  easily  in  water, 
in  ice,  and  in  salts  containing  water  of  crystallisa- 
tion, as  Glauber's  salt,  copper  sulphate,  magnesium 
sulphate,  borax,  etc. 

According  to  Roscoe  and  Dittmar,  1  volume  -of 
water  dissolves  at  0°,  503  volumes  of  the  gas.  The 
parts  by  weight  of  the  gas  which  dissolve  in  1  g. 
of  water  at  a  pressure  of  760  mm.  and  at  different 
temperatures,  are  given  in  the  following  table  :  — 

Temperature        HC1  Temperature         HC1 

0  0.825  32  0.665 

4  0.804  36  0.649 

8  0.783  40  0.633 

12  0.762  44  0.618 

16  0.742  48  0.603 

20  0.721  52  0.589 

24  0.700  56  0.575 

28  0.682  60  0.561 

At  ordinary  temperatures,  1  volume  of  alcohol  dis- 
solves 327  volumes  of  hydrochloric  acid. 

At  a  pressure  of  from  30  to  40  atmospheres,  the 
gas  condenses  to  a  colourless  liquid  of  strong  refrac- 
tive power. 

If  no  other  acid  gas  is  present  with  the  hydro- 
chloric acid,  it  can  be  determined  by  drawing  a 
measured  quantity  of  the  gas  through  a  standardised 
solution  of  an  alkali  and  titrating  back  with  an  acid. 

Hydrochloric  acid  may  be  accurately  determined 
by  absorbing  it  with  an  alkaline  solution  free  from 
chlorine,  and,  after  acidifying,  precipitating  it  with 
silver  nitrate,  and  weighing  as  silver  chloride. 

A  method  proposed  by  Cl.  Winkler,1  and  based 

1  Cl.  Winkler,  Anleitung  zur  Untersuchung  der  Industrie-Gase, 
Part  II,  p.  322. 


248  GAS  ANALYSIS  PART  n 

upon  J.  Volhard's  volumetric  method  for  the  deter- 
mination of  silver,1  consists  in  placing  in  a  suitable 
absorption  apparatus  a  few  drops  of  ammonium 
sulphocyanate  or  potassium  sulphocyanate,  some  iron 
alum  solution,  and  a  measured  amount  of  ^  silver 
nitrate  solution.  Upon  leading  the  gas  through  this 
solution  the  hydrochloric  acid  unites  with  the  silver, 
forming  silver  chloride.  The  end  of  the  reaction  is 
shown  by  the  blood-red  colour.  The  cause  of  this 
colour  is,  that  after  all  of  the  silver  nitrate  has  been 
changed  to  silver  chloride,  the  silver  sulphocyanate 
present  is  also  decomposed  and  ferric  sulphocyanate 
is  formed.  The  volume  of  the  gas  is  measured  and  the 
amount  of  hydrochloric  acid  it  contains  is  calculated. 

SILICON  TETRAFLUORIDE  (SiF4) 

Specific  gravity,  3.60469;  weight  of  1  liter,  4.66414. 

2  vol.  SiF4  =  1  vol.  Si  +  4  vol.  F. 

The  gas  is  completely  taken  up  by  water,  being  at 
the  same  time  decomposed  — 

3  SiF4  +  4H2O  =  Si(OH)4  +  2H2SiF6. 

This  reaction,  which  has  been  employed  by  R. 
Fresenius2  for  the  quantitative  determination  of 
fluorine,  might  possibly  be  made  use  of  for  the  deter- 
mination of  silicon  tetrafluoride  in  gases  ;  up  to  the 
present  time,  however,  no  satisfactory  method  has 
been  devised.  The  silicon  tetrafluoride  probably 

1  J.  Volhard,  Zeitschrift  fur  analyt.  Chemie,  13,  171,  and  17, 
482. 

2  Fresenius,  Quant,  chemische  Analyse,  6th  ed.,  Part  I,  p.  431. 


CHAP,  iv         DETERMINATION   OF  PHOSPHINE  249 

formed  in  fusion  processes  is  always  mixed  with 
large  amounts  of  steam,  dust,  and  sulphur  dioxide, 
and  for  these  reasons  its  determination  is  exception- 
ally difficult. 

PHOSPHINE  (PH3) 

Specific  gravity,  1.17552;  'weight  of  1  liter,  1.52102. 
2  vol.  PH3  =  i  vol.  P  +  3  vol.  H. 

Phosphine  is  a  colourless  gas  with  a  very  unpleasant 
odour,  resembling  that  of  decayed  fish.  It  is  very 
poisonous.  The  pure  gas  takes  fire  only  at  a  tem- 
perature above  100°,  but  the  friction  of  the  stopper 
of  the  bottle  containing  the  gas  is  often  sufficient  to 
ignite  it. 

It  can  be  mixed  with  pure  oxygen  without  change, 
but  if  the  mixture  be  suddenly  brought  under  di- 
minished pressure,  it  explodes.  Phosphine  takes  fire 
when  brought  in  contact  with  a  drop  of  fuming  nitric 
acid,  or  with  the  vapour  of  chlorine  or  bromine. 

Phosphine  is  somewhat  soluble  in  water.  One 
volume  of  water  absorbs  about  0.02  volume  of  the 
gas,  and  takes  on  its  odour  and  disgusting  taste. 
Exposed  to  the  light,  the  solution  decomposes  with 
evolution  of  hydrogen  and  separation  of  amorphous 
phosphorus.  The  gas  is  decomposed  by  electric 
sparks  into  phosphorus  and  hydrogen,  the  resulting 
volume  being  exactly  1^  times  that  at  the  beginning. 

Phosphine  combines,  as  does  ammonia,  with  metal- 
lic chlorides,  aluminium  chloride,  tin  chloride,  and 
antimony  chloride. 

The  gas  cannot  be  detected  by  means  of  lead- 
paper,  but  strips  of  paper  impregnated  with  silver 


250  GAS   ANALYSIS  PART  n 

nitrate  are  turned  black  at  once,  metallic  silver 
separating  out  and  phosphoric  acid  being  formed. 

Phosphine  can  be  determined  by  drawing  the  gas 
in  question  through  bromine  water  and  then  pre- 
cipitating the  resulting  phosphoric  acid  by  magnesia 
mixture.  If  a  silver  solution  has  been  used  for  the 
absorption,  the  excess  of  silver  must  first  be  removed 
by  hydrochloric  acid. 

The  phosphoric  acid  thus  formed  may  also  be  de- 
tected with  ammonium  molybdate. 

According  to  J.  Riban  l  a  hydrochloric  acid  solu- 
tion of  cuprous  chloride  absorbs  phosphine. 

The  best  absorbent  for  determining  phosphine  in 
the  presence  of  acetylene  is  a  solution  of  copper  sul- 
phate containing  free  sulphuric  acid.2  (See  p.  316.) 

ARSINE  (AsH3) 

Specific  gravity,  2.69728;  weight  of  1  liter,  3.49003. 
2  vol.  AsH3  =  J  vol.  As  +  3  vol.  H. 

Arsine  is  a  colourless  gas  of  very  unpleasant  odour. 
It  burns  with  a  blue  flame,  with  formation  of  white 
clouds  of  arsenic  trioxide.  When  passed  through  a 
highly  heated  tube,  the  gas  is  decomposed  and  a 
glistening  mirror  of  metallic  arsenic  is  deposited. 

When  arsine  is  led  over  red-hot  copper  oxide, 
water  and  copper  arsenide  are  formed.  Arsine  may 
be  easily  detected  in  this  manner.  If  arsine  is  passed 
over  heated  metals,  such  as  tin,  potassium,  or  sodium, 
arsenides  are  formed  and  hydrogen  is  set  free. 

1  Compt.  rend.,  88,  581. 

2  Hempel  and  Kahl,  Zeitschr.  f.  angew.  Chemie,  1898,  p.  53. 


CHAP,  iv  DETERMINATION  OF   STIBINE  251 

Arsine  precipitates  the  metal  from  solutions  of 
gold  and  silver  salts  — 

AsH3+6AgN03  +  3H20  =  As(OH)3  +  6HN03  +  6Ag, 

and  if  an  aqueous  solution  of  ammonia  be  carefully 
added  to  the  filtrate,  a  yellow  ring  of  silver  arsenite 
is  formed.  Minute  quantities  of  arsenic  may  be  de- 
tected in  this  manner. 

Water  absorbs  five  times  its  volume  of  arsine. 

Bromine,  chlorine,  and  iodine  decompose  the  gas. 

A  very  suitable  method  for  the  determination  of 
arsine  consists  in  leading  it  into  a  silver  solution, 
precipitating  the  excess  of  silver  by  hydrochloric 
acid,  filtering,  and,  after  warming,  precipitating  the 
arsenic  with  magnesia  mixture.  The  precipitate  is 
ignited  and  weighed  as  Mg2As2O7. 

Arsine  can  be  completely  removed  from  hydrogen 
sulphide  by  leading  the  mixture  of  the  two  gases 
through  a  tube  which  contains  pieces  of  iodine. 

STIBINE  (SbH3) 

Specific  gravity,  4.3287  ;  weight  of  1  liter,  5.6. 
2  vol.  SbH3  =  i  vol.  Sb  +  3  vol.  H. 

Water  absorbs  from  4  to  5  volumes  of  the  gas  at 
10°.  Stibine  burns  with  a  greenish  flame,  and  gives 
off  white  fumes  of  antimony  trioxide. 

If  the  gas  be  led  through  glass  tubes  heated  to 
redness,  metallic  antimony  is  deposited  in  the  form 
of  a  mirror  a  short  distance  beyond  the  heated  point. 

If  stibine  be  passed  into  a  solution  of  silver  nitrate, 
black  silver  antimonide,  SbAg3,  mixed  with  metallic 
silver,  is  precipitated. 


252  GAS   ANALYSIS  PART  n 

Sulphur,  when  exposed  to  the  light,  or  when  heated 
to  above  100°,  decomposes  the  gas  and  becomes  coated 
with  orange-red  antimony  sulphide  — 

2  SbH3  +  68  =  Sb2S3  +  3  H2S. 

Hydrogen  sulphide  acts  similarly  in  the  light  — 

2  SbH3  +  3  H2S  =  Sb2S3  +  6  H2. 

Concentrated  nitric  acid  and  potassium  perman- 
ganate oxidise  the  gas.  Stibine  does  not  blacken 
lead-paper. 

Stibine  may  be  determined  by  leading  the  gas 
under  examination  into  a  silver  solution,  filtering  off 
the  silver  antimonide  formed,  and  digesting  it  with 
ammonium  sulphide.  The  antimony  goes  into  solu- 
tion as  ammonium  sulphantimonite,  and  after  being 
thrown  down  again,  it  can  be  weighed  as  antimony 
sulphide,  or  it  may  be  converted  into  antimony 
tetroxide  and  weighed  as  such. 


PART   III 

PKACTICAL  APPLICATIONS  OF 
GAS  ANALYSIS 


CHAPTER   I 
COMBUSTION  GASES    -FURNACE  GASES 

IN  many  industries  the  profits  are  largely  depend- 
ent upon  the  amounts  paid  out  for  fuel,  ?o  that  in  all 
factories  having  large  furnaces  a  systematic  exami- 
nation of  the  working  of  the  furnace  is  of  considera- 
ble importance.  The  driving  of  a  fire  is  the  more 
favourable  the  less  the  excess  of  air  beyond  the 
amount  necessary  for  producing  complete  combus- 
tion. In  many  boiler  plants  which  seem  to  be  other- 
wise well  constructed,  the  examination  shows  that  an 
enormous  excess  of  air  is  being  used,  and  that  a  cor- 
respondingly large  amount  of  heat  is  being  allowed 
to  pass  unused  into  the  chimney.  It  is  impracticable 
to  wholly  abstract  the  heat  from  the  gases  from  the 
fire ;  a  certain  amount  of  heat  must  be  left  in  them, 
so  that  they  will  move  rapidly  enough  in  the  chim- 
ney. It  follows  that  a  disproportionately  large 
amount  of  heat  will  be  lost  when  the  draught  in  the 
furnace  is  too  strong.  Even  the  most  skilful  stoker 
will  not  be  able  to  tell  merely  from  the  appearance 
of  the  fire  exactly  how  the  combustion  is  proceed- 
ing. For  these  reasons  it  is  advisable  to  adopt  some 
arrangement  which  will  continually  draw  off  a  small 
current  of  gas  from  the  fire,  and  to  give  the  stoker 
a  bonus  which  is  higher  the  less  oxygen  there  is  in 
the  departing  gases. 

255 


256 


GAS  ANALYSIS 


PART  III 


To  judge  of  the  combustion,  it  is  quite  sufficient 
to  make  merely  a  determination  of  the  oxygen,  for 
the  amounts  of  all  other  products  of  combustion  are 

of  course  depend- 
ent upon  the  oxy- 
gen, provided  that 
the  furnace  is  not 
giving  off  thick 
clouds  of  smoke, 
i.e.  that,  instead 
of  burning,  the 
fire  merely  smoul- 
ders. 

The  tube  for 
taking  off  the 
gases  is  intro- 
duced into  the 
flue  at  a  place 
which  is  selected 
with  reference  to 
the  points  men- 
tioned on  p.  3. 
It  is  convenient 
to  connect  the 
tube  with  a  bot- 
tle aspirator  made 
of  ordinary  sheet- 
FIG.  88.  zinc  (see  Fig.  83) . 

The  water  is  al- 
lowed to  drop  from  A  into  B,  and  its  flow  can  easily 
be  so  regulated  that  the  water  will  flow  out  of  A 
once  in  six,  twelve,  or  twenty-four  hours.  The 
analysis  of  this  gas  sample  gives  the  average  com- 


CHAP,  i      COMBUSTION   GASES  — FURNACE   GASES        257 

position  of  the  furnace  gases.  The  tube  d,  which 
reaches  to  about  the  middle  of  A,  serves  for  taking 
off  samples  with  the  gas  burette. 

Well-managed  furnaces  should  give  not  more  than 
about  8  per  cent  of  free  oxygen.  The  furnaces  of 
the  present  day  may  be  said  to  be  exceptionally  good 
when  the  gases  from  the  fire  contain  only  from  3  to 
4  per  cent  of  oxygen. 

If  a  more  complete  analysis  of  the  furnace  gases 
is  desired,  the  procedure  is  exactly  the  same  as  that 
given  for  the  analysis  of  generator  gases. 

Furnace  gases  usually  contain  only  carbon  dioxide, 
oxygen,  and  nitrogen.  All  other  gases  are  present 
in  but  very  small  amounts.  In  oft-repeated  analyses 
the  author  has  always  found  only  traces  of  carbon 
monoxide,  methane,  and  the  heavy  hydro-carbons. 

The  apparatus  necessary  for  thus  controlling  the 
working  of  a  furnace  is  — 

1.  A  bottle  aspirator,  with  the  necessary  tubes, 
for  collecting  the  gas. 

2.  A  simple  gas  burette. 

3.  A  pipette  for  solid  absorbents,  which  is  filled 
with  phosphorus  and  kept  in  a  light-tight  box. 

The  analysis  of  a  gas  mixture  from  a  furnace  may 
also  be  made  with  the  Orsat  apparatus.  Many  modi- 
fications of  this  have  been  devised,  but  the  form  shown 
in  Fig.  84,  is  that  most  generally  used.  It  consists 
of  the  measuring  burette  a  containing  100  ccm.,  and 
of  the  absorption  bulbs  5,  <?,  and  d.  The  burette  is 
joined  at  the  lower  end  with  a  level-bulb  and  at  the 
upper  end  with  a  long  capillary  tube  which  has  three 
branch  tubes,  each  supplied  with  a  glass  stopcock. 
The  absorption  bulbs  are  connected  to  these  branch 


258  GAS  ANALYSIS  PART  m 

tubes  in  the  manner  shown  in  the  figure  and  are 
usually  filled  with  glass  tubes  which  serve  to  bring 
the  various  reagents  into  intimate  contact  with  the 
gas  mixture.  The  absorption  bulb  b  contains  a 
concentrated  solution  of  potassium  hydroxide  for 
the  absorption  of  carbon  dioxide,  c  contains  an 
alkaline  solution  of  pyrogallol,  while  d  is  filled  with 
a  hydrochloric  acid  solution  of  cuprous  chloride. 
The  gas  mixture  which  is  to  be  analysed  is  drawn 
into  the  apparatus  through  the  outer  end  of  the 
capillary  by  first  opening  the  stopcock  k,  raising  the 
level-bulb  until  the  burette  and  the  capillary  are 
filled  with  water,  and  then  lowering  the  level-bulb, 
the  stopcock  k  being,  of  course,  closed  after  the  gas 
has  been  drawn  in.  Before  beginning  the  operation 
the  reagents  in  the  three  absorption  bulbs  should 
first  be  drawn  up  to  marks  on  the  capillary  tubes 
above  the  bulbs.  It  is  convenient  to  work  with  a 
sample  of  exactly  100  ccm.,  this  being  measured  off 
in  the  manner  described  for  the  Hempel  apparatus 
on  p.  37.  The  gas  is  then  first  driven  over  into 
b  to  absorb  carbon  dioxide  and  is  drawn  back  into 
the  burette  and  measured.  The  reagent  in  the 
absorption  bulb  must,  of  course,  be  brought  to  the 
height  at  which  it  first  stood.  After  the  carbon 
dioxide  has  been  thus  determined,  the  gas  is  passed 
over  into  the  second  absorption  bulb  and  oxygen  is 
removed,  and  finally  the  carbon  dioxide  is  absorbed 
in  the  third  bulb.  Some  forms  of  the  Orsat  appara- 
tus are  supplied  also  with  a  palladium  asbestos  tube 
/,  for  the  determination  of  the  combustible  gases. 

The  Orsat  apparatus  is  quite  extensively  used  at 
the  present  time,  because  it  is  easy  to  manipulate 


\ 


FIG.  84. 


260  GAS   ANALYSIS  PART  in 

and  is  so  compact  that  it  can  conveniently  be  carried 
about.  It  cannot,  however,  be  recommended  because, 
first,  the  long  capillary  connection  between  the  burette 
and  the  absorption  bulb  contains  a  volume  of  gas 
sufficient  to  seriously  influence  the  accuracy  of  the 
work  ;  second,  the  long  capillary  tube  with  its  branch 
tubes  and  glass  stopcocks  is  fragile  and  costly,  and  if 
it  is  broken  it  can  be  repaired  only  by  an  expert-glass 
blower  ;  third,  the  reagents  in  the  second  and  third 
absorption  bulbs  are  not  fully  protected  from  the 
action  of  the  air  and  consequently  deteriorate  rapidly 
(some  manufacturers  attach  thin  rubber  bulbs  to  the 
open  end  of  the  absorption  bulb  to  protect  the  reagent 
from  the  air,  but  these  rubber  bulbs  are  most  unsatis- 
factory) ;  and  fourth,  and  most  important  of  all,  the 
apparatus  does  not  permit  of  the  reagent  in  the  second 
and  third  bulb  being  shaken  with  the  gas  mixture, 
the  result  being  that  the  absorption  of  oxygen  and 
carbon  monoxide  takes  place  very  slowly  and  is  rarely 
complete.  A  comparison  of  various  methods  for 
determining  carbon  monoxide1  gave  the  following 
results  for  the  Or  sat  apparatus :  — 


Gas  mixture  contained 

Average  of  Six  De- 
terminations     with 
the  Orsat  Apparatus 

3  per  cent  carbon  monoxide      .... 
9        "             "              "             .... 
15                      «              «             .... 

2.31  per  cent 
8.50 
14.40       « 

An  idea  of  the  completeness  of  the  combustion  in 
a  heating  plant  may  be  obtained  in  a  moment  with- 

1  Dennis  and  Edgar,  J.  Am.  Chem.  Soc.,  19,  859. 


CHAP,  i       COMBUSTION  GASES  — FURNACE   GASES        261 

out  the  aid  of  a  chemical  examination  bj  using  an 
apparatus  which  shows  the  specific  gravity  of  the 
escaping  gases.  The  gases  in  question  are  continu- 
ously drawn  through  the  apparatus  by  means  of  a 


FIG.  85. 


steam  or  water  suction  pump,  but  before  entering 
they  must  pass  through  a  cotton  filter  to  remove  flue 
dust  and  soot,  and  must  be  freed  from  moisture  by 
means  of  calcium  chloride. 


262  GAS   ANALYSIS  PART  m 

The  apparatus  for  determining  the  specific  gravity 
of  gases  in  this  manner  is  termed  a  gas  balance.  A 
number  of  different  forms  have  been  devised.  In 
addition  to  the  one  to  be  described  on  p.  273,  Fig.  89, 
which  was  devised  by  Lux,  the  gas  balance  original 
with  Arndt  has  been  found  to  be  quite  satisfac- 
tory (Fig.  85).  This  consists  essentially  of  a  fine 
balance,  carrying  on  one  end  of  the  beam  a  closed 
glass  vessel,  pan,  and  weights,  while  to  the  other 
beam  end  is  attached  an  open  glass  vessel  (shaded 
in  the  figure)  through  which  passes  the  gas  mixture 
which  is  being  examined,  the  gas  entering  through 
tube  2  and  passing  out  through  tube  3. 

Such  balances  will  not,  of  course,  correctly  show 
the  presence  of  unburned  gases. 

With  normal  working  of  the  heating  plant  these 
gas  balances  are  convenient  and  fairly  accurate;  but 
if  variations  from  the  normal  occur  in  the  firing,  they 
do  not  give  satisfactory  results. 


CHAPTER   II 
ILLUMINATING  GAS 

WATER  GAS  —  GENERATOR  GAS  —  BLAST-FUR- 
NACE GASES  —  COKE-FURNACE  GASES 

THE  gases  formed  in  dry  distillation  of  coal  are 
quantitatively  of  very  different  composition.  All  of 
them  contain  hydrocarbon  vapours,  carbon  dioxide, 
carbon  monoxide,  heavy  hydrocarbons,  marsh-gas,  hy- 
drogen, water,  and  nitrogen,  and  most  of  them  con- 
tain also  some  oxygen  which  has  entered  through 
leakages  in  the  apparatus. 

The  unpurified  gas  contains  hydrogen  sulphide, 
ammonia,  uncondensed  tar,  as  well  as  carbon  disul- 
phide  and  organic  sulphur  compounds. 

In  the  examination  of  illuminating  gas  there  must 
be  made  — 

1.  A  photometric  measurement  of  the  illuminating 
power  of  the  gas. 

2.  The  determination  of  the  specific  gravity  of  the 
gas. 

3.  The  determination  of  tar  and  the  constituents 
separable  by  cooling. 

4.  The  volumetric  analysis  of  the  gaseous  con- 
stituents. 


264  GAS   ANALYSIS  PART  in 

5.  The  determination  of  sulphur. 

6.  The  determination  of  ammonia. 

7.  The  determination  of  carbon  dioxide. 

1.    The  Measurement  of  the  Illuminating  Power 

The  amount  of  light  generated  by  an  illuminating 
gas  in  burning  is  dependent  upon  the  construction 
of  the  burner,  so  that  this  determination  is  accom- 
panied by  large  errors. 

Up  to  the  present  time  there  exists  no  perfectly 
accurate  and  simple  method  for  determining  the 
illuminating  power  of  a  flame.  When  we  remember 
that  the  light  given  out  by  ordinary  lamps  is  com- 
posed of  a  great  number  of  rays  of  different  colours 
which  result  from  their  different  wave-lengths,  and 
which  cannot  be  directly  compared  with  one  another, 
it  is  easy  to  understand  that  the  results  of  the 
determinations  are,  under  certain  conditions,  quite 
variable. 

If  candle  flames  and  gas  flames  are  compared,  the 
photometric  measurements  agree  quite  satisfactorily. 
If,  however,  the  yellow  light  of  a  candle  be  compared 
with  the  white  light  of  a  Siemens  regenerative 
burner,  an  electric  lamp,  or  an  Auer  von  Welsbach 
incandescent  light,  one  will  find  it  quite  impossible 
to  make  even  approximately  accurate  measurements, 
and  the  uncertainty  in  the  determination  will  amount 
to  more  than  a  whole  candle  power.  The  explana- 
tion of  this  is,  that  while  similarly  coloured  sources 
of  light  may  be  directly  measured  in  the  photometer, 
lights  of  different  colours  cannot  be  compared  with 
one  another.  The  electric  light,  which  is  rich  in  blue 


CHAP,  ii  ILLUMINATING  GAS  265 

rays,  cannot  be  compared  with  a  candle  flame,  which 
possesses  but  few  of  these  rays.  The  coloured  rays 
are  not  of  equal  value  for  purposes  of  illumination, 
and  a  correct  idea  of  the  lighting  power  of  any  appli- 
ance can  be  obtained  only  by  breaking  up  the  light 
by  means  of  a  spectro-photometer,  and  then  ascer- 
taining how  much  of  each  sort  of  light  is  present. 
Several  spectro-photometers  for  purely  scientific 
researches  have  been  devised. 

For  controlling  the  working  of  gasworks,  the 
measurement  of  illuminating  power  is  nevertheless 
of  great  value,  because  it  can  be  quickly  made.  But 
it  should  not  be  forgotten  that  only  gases  of  similar 
composition  can  be  compared  with  one  another.  If 
one  wished  to  compare  oil-gas  with  ordinary  illumi- 
nating gas,  he  would  immediately  be  confronted  by 
the  difficulty  that  there  is  no  burner  in  which  both 
gases  can  be  burned  with  equal  advantage.  For  this 
reason  the  kind  of  burner  in  which  the  gas  was 
burned  should  be  exactly  stated  in  all  photometric 
measurements. 

For  ordinary  illuminating  gas  the  so-called  normal 
burner  of  Elsler  has  been  adopted  in  Germany.  This 
is  an  Argand  burner  consuming  150  liters  per  hour, 
and  which  must  show,  when  burning,  a  pressure  of 
2.5  mm.  in  the  burner. 

The  unit  of  light  in  use  in  Germany  is  a  candle  of 
paraffin  with  melting-point  55°  C.  The  candle  has 
a  diameter  of  20  mm.,  and  six  of  them  weigh  500  g. 
The  wick,  which  weighs  0.668  g.  per  meter,  consists 
of  twenty -four  cotton  threads,  one  of  which  is  red  so 
that  the  candles  may  be  easily  distinguished.  The 
height  of  the  flame  is  50  mm. 


266 


GAS  ANALYSIS 


PART  III 


Instead  of  this  candle  an  amyl  acetate  lamp  of  the 
Hafner-Alteneck  construction  is  sometimes  used.  An 
advantage  possessed  by  the  amyl  acetate  lamp  is,  that 
when  once  it  has  been  regulated  it  burns  without 
change  for  a  long  time,  while,  with  a  candle,  the 
height  of  the  flame  must  be  constantly  regulated  by 
cutting  off  the  wick.  1000  of  the  above  candles  are 


FIG.  86. 

equal  to  977  of  the  English  spermaceti  candles,  and 
to  102  Paris  Car  eel-lamps. 

The  measurement  of  the  illuminating  power  may 
be  made  with  a  Bunsen  photometer  (Fig.  86).  This 
consists  of  a  partly  translucent  screen  of  paper,  which 
can  be  moved  back  and  forth  between  the  normal 
light  and  the  flame  under  examination.  In  measur- 
ing, the  screen  is  brought  into  such  a  position  that 


CHAP,  ii  ILLUMINATING  GAS  267 

the  translucent  spot  appears  equally  dark  on  both 
sides,  the  observation  being  easily  made  by  means  of 
two  mirrors  in  B,  placed  at  the  proper  angles. 

In  this  position  the  screen  is  illuminated  with 
equal  intensity  by  the  two  sources  of  light.  The 
ratio  between  the  illuminating  power  ef  the  flame 
that  is  being  tested  and  that  of  the  normal  flame,  is 
as  the  squares  of  the  distances  of  the  flames  from  the 
screen. 

The  photometer  is  usually  so  arranged  that  the 
normal  flame  is  fastened,  at  a  definite  distance  from 
the  screen,  to  a  slide  which  moves  along  a  track. 
On  this  track  is  a  scale,  from  which  the  illuminating 
power  may  be  directly  read  off. 

The  paper  screen  is  best  made  from  fine  white 
drawing-paper  that  does  not  glisten,  and  that  is 
about  as  thick  as  ordinary  writing-paper.  A  cork  is 
dipped  into  molten  paraffin,  stearin,  or  spermaceti, 
and  is  then  pressed  upon  the  middle  of  the  paper. 
When  the  fat  has  cooled  it  is  scraped  off  with 
a  knife,  and  the  paper  is  warmed  until  the  spot 
appears  uniformly  translucent.  If  it  is  too  nearly 
transparent,  the  paper  is  laid  between  two  sheets 
of  clean  blotting-paper  and  pressed  with  a  warm 
flat-iron. 

The  photometer  has  been  improved,1  the  fat  spot 
being  replaced  by  an  optical  arrangement  consisting 
essentially  of  two  prisms,  by  means  of  which  the 
light  from  one  source  appears  as  a  spot  surrounded 
by  the  light  from  the  other  source.  In  this  way  a 

1  O.  Lummer  and  E.  Brodhun,  "Ersatz  des  Photometerfettflecks 
durch  eine  rein  optische  Vorrichtung,"  Zeitschrift  fur  Instrumen- 
tenkunde,  1889,  pp.  23  and  41. 


268  GAS   ANALYSIS  PART  m 

very  sharp  comparison  of  the  illuminating  powers  of 
the  two  flames  is  made  possible. 

To  determine  the  candle  power  of  an  illuminating 
gas,  the  consumption  of  the  flame  is  first  brought  to 
150  liters  per  hour  by  means  of  an  experimental  gas- 
meter.  The  flame  of  the  normal  candle  or  amyl  ace- 
tate lamp  having  been  brought  to  the  proper  height, 
the  photometric  measurement  is  made. 

The  measurement  should  be  made  in  a  room  with 
blackened  walls,  and  with  windows  which  can  be 
covered  light-tight  by  black  curtains.  The  room 
itself  should  be  dry  and  well  ventilated,  since  the 
accumulation  of  carbon  dioxide  changes  considerably 
the  illuminating  power  of  a  flame.  The  gas  passing 
to  the  normal  burner  must  never  be  led  through  long 
pieces  of  rubber  tubing,  because  they  would  change 
its  illuminating  power. 

Unless  the  gas-meter  is  in  constant  use,  the  gas 
must  burn  in  the  normal  burner  for  at  least  two 
hours  before  the  measurement  is  made.1 


2.    The  Determination  of  the  Specific  Gravity 

The  determination  of  the  specific  gravity  is  most 
conveniently  made  by  Bunsen's  method 2  of  measur- 
ing the  speed  of  escape  of  the  gas. 

This  method  is  based  upon  the  fact  that  the 
specific  gravities  of  two  gases  escaping  through 
narrow  openings  in  thin  plates  bear  nearly  the 
same  ratio  to  each  other  as  the  squares  of  their 

1  Given  in  detail  in  N.  H.  Schilling's  Handbuch  far  Steinkohlen- 
gas-Beleuchtung. 

2  Bunsen,  Gasometrische  Methoden,  2d  ed.,  p.  184. 


CHAP,  ii  ILLUMINATING   GAS  269 

speeds  of  escape.  If  a  gas  of  the  specific  gravity 
s  has  a  speed  of  flow  f,  and  another  gas  of  a  spe- 
cific gravity  sx  has  a  speed  of  flow  tv  the  relation 
between  the  speed  of  escape  and  the  specific  gravity 
is  given  by  the  equation  — 


If  s  or  the  specific  gravity  of  one  of  the  gases 
be  regarded  as  1,  the  specific  gravity  of  the  other 
gas  is  found  by  the  formula  — 


=  *. 


Figure  87  shows  the  apparatus  used  for  this  deter- 
mination. A  glass  tube  of  about  70  ccm.  capacity 
is  luted  into  the  iron  cap  A.  This  cap  is  fitted  with 
a  three-way  stopcock  by  means  of  which  the  inside 
of  the  glass  tube  can  be  brought  into  communication 
with  either  the  tube  B,  through  which  the  gases  are 
introduced,  or  the  small  opening  in  C.  This  opening 
is  made  in  a  platinum  plate,  which  is  about  as  thick 
as  tin  foil,  and  is  luted  in  position.  To  obtain  a 
platinum  plate  as  thin  and  an  opening  as  small  as 
possible,  the  platinum  foil  is  pierced  with  a  fine 
sewing  needle,  and  is  hammered  with  a  polished 
hammer  upon  a  polished  anvil  until  the  opening  can 
no  longer  be  seen  with  the  naked  eye,  and  is  only 
visible  when  the  plate  is  held  between  the  eye  and  a 
bright  flame.  The  plate  thus  perforated  is  cut  out 
in  the  form  of  a  small  circular  disk,  the  opening 
being  at  the  centre. 


270 


GAS  ANALYSIS 


In  order  that  the  gases  to  be  examined  may  always 
escape  through  the  opening  0  under  the  same  con- 
ditions as  regards  pressure, 
there  is  placed  in  A  a  float 
bb.  This  float  should  be  as 
light  as  possible,  and  for  this 
reason  it  is  best  made  from  a 
very  thin-walled  glass  tube. 
The  float  has  at  £  a  little 
button  of  black  glass  from 
which  projects  a  small,  white 
glass  point. 

Two  fine  threads  of  black 
glass,  /3j  and  /32,  are  fused 
around  the  lower  part  of  the 
stem  of  the  float.  These  two 
threads,  together  with  the 
black  glass  button  at  the  top, 
serve  as  marks. 

If  the  tube  containing  the 
gas  be  pushed  down  so  far 
into  the  mercury  that  a  mark 
on  the  glass  is  tangent  to  the 
outer  mercury  surface,  then 
the  float  which  is  inside  the  tube  is  no  longer  visible 
through  the  telescope. 

If  now  the  stopcock  be  opened  and  the  gas  allowed 
to  escape  through  the  opening  in  the  platinum  plate, 
the  float  rises,  being  carried  up  upon  the  surface  of 
the  mercury  in  the  tube.  If  the  level  of  the  external 
mercury  be  observed  through  the  telescope,  the  white 
glass  tip  of  the  float  soon  comes  into  the  field,  and 
informs  the  observer  that  the  black  button  yS  will 


FIG.  ST. 


CHAP.  II 


ILLUMINATING   GAS 


271 


shortly  appear.  When  this  comes  in  sight  the  time 
is  taken,  the  end  of  the  timing  being  at  that  moment 
at  which  the  mark  yS2  comes 
into  the  field  of  the  tele- 
scope ;  the  near  approach  of 
/32  is  here  shown  by  the 
appearance  of  ftr 

From  these  observations 
is  obtained  the  rapidity  of 
escape  of  a  column  of  gas 
which,  measured  from  &  has 
the  length  shown  by  the 
marks  /3/32  on  the  float ; 
moreover,  the  gases  escape 
under  the  same  differences  of 
pressure  in  all  of  the  experi- 
ments. The  times  taken  by 
the  different  gases  to  escape 
through  the  fine  opening  in 
O  give,  when  squared,  the 
ratios  of  the  specific  gravi- 
ties of  the  gases. 

The  gases  must  be  dried, 
and  the  mercury  must  be 
pure  and  dry.  An  advan- 
tage of  the  Bunsen  appara- 
tus is  that  a  determination  can  be  made  with  a  very 
small  quantity  of  the  gas. 

N.  H.  Schilling  has  given  the  apparatus  a  very 
practical  form  for  the  examination  of  illuminating 
gas,  where  large  amounts  of  the  gas  are  usually 
available. 

A  (Fig.  88)  is  a  glass  tube   of  40  mm.  internal 


FIG.  88. 


272  GAS  ANALYSIS  PART  jn 

diameter  and  about  450  mm.  long.  The  upper  end 
is  luted  into  a  brass  cover  into  which  is  inserted  the 
tube  a  through  which  the  gas  is  led  in.  In  the  middle 
of  the  plate  is  the  escape  tube  6,  and  through  another 
opening  passes  a  thermometer.  On  the  end  of  b  is  the 
perforated  platinum  plate.  The  inner  cylinder  has 
two  marks,  CO.  The  apparatus  is  filled  with  water. 

To  determine  the  specific  gravity  of  an  illuminat- 
ing gas  with  this  apparatus,  the  tube  is  first  filled 
with  air,  and  the  time  of  escape  of  the  air,  under  the 
prevailing  temperature  and  pressure,  is  noted.  The 
last  trace  of  air  is  then  removed  by  repeated  draw- 
ing in  and  driving  out  the  gas  to  be  examined,  and 
the  time  of  escape  of  the  illuminating  gas  is  then 
observed.  The  squares  of  the  values  are  directly 
proportional  to  the  specific  gravities  of  the  gases. 
Since  the  specific  gravity  of  air  is  usually  taken  as  1, 
the  calculation  is  very  simple. 

A  very  convenient  arrangement  for  the  continuous 
and  direct  determination  of  the  specific  gravity  is 
the  gas-balance  of  Friedrich  Lux.1 

The  instrument  (Fig.  89)  consists  of  a  large  bulb 
A,  which  is  attached  to  one  end  of  a  lever,  the  other 
end  gives  directly  on  a  scale  the  specific  gravity  of 
the  gas.  The  lever  is  so  made  that  the  gas  to  be 
examined  can  be  led  through  the  tube  b  and  through 
the  hollow  support  into  the  bulb.  The  gas  passes 
off  through  a  second  tube,  which  is  also  connected 
with  the  fulcrum  of  the  lever.  If  a  number  of  such 
balances  are  joined  together,  and  if,  between  the 
balances,  absorption  apparatus  for  the  various  con- 
stituents is  introduced,  the  composition  of  the  gas 

1  To  be  obtained  from  Friedrich  Lux,  Ludwigshafen,  Germany. 


CHAP.  II 


ILLUMINATING  GAS 


273 


can  be  read  off  directly  from  the  positions  of  the 
different  pointers.  For  use  of  this  sort,  Lux  has 
devised  a  balance  with  two  bulbs,  by  means  of  which 
the  amount  of  one  constituent  in  the  gas  can  be 
directly  read  off. 

The  results    obtained   by  this  instrument  are  of 
course  influenced  by  the  temperature  and  the  varia- 


FIG.  89. 

tions  of  pressure,  but  nevertheless  the  apparatus  is 
very  well  adapted  for  controlling  the  working  of  a 
gas  plant. 

3.    The  Determination  of  Tar,  etc. 

For  the  determination  of  tar  in  unwashed  gases, 
F.  Tieftrunk  uses  the  apparatus  shown  in  Fig.  90. 
Winkler  l  describes  this  as  follows  :  — 

1  Cl.  Winkler,  Anleitung  zur  Untersuchung  der  Industrie- Gase, 
Part  II,  p.  52. 


274 


GAS   ANALYSIS 


"  The  glass  cylinder  A.  has  a  brass  rim,  and  it  can 
be  tightly  closed  by  means  of  a  plate  which  is 
fastened  with  screws.  To  the  tube  c  is  attached  a 
bell-shaped  device  A,  which  consists  of  perforated 
sheets  of  brass  slipped  over  the  tube.  The  distance 
between  the  rows  of  holes  and  also  between  the  holes 
themselves  is  about  5  mm.  The  glass  cylinder  A  is 


.    ,         FIG.  90. 

filled  somewhat  more  than  half  full  of  alcohol  of  from 
25  to  29  per  cent  by  weight,  the  bell  being  entirely 
covered  by  the  liquid.  The  alcohol  takes  up  the  tar 
which  enters,  but  is  said  to  hold  back  only  traces  of 
other  constituents,  such  as  benzene  and  naphthalene. 
"The  U-tube  B  is  12  mm.  in  diameter  and  10  cm. 
long,  and  is  filled  with  cotton.  C  is  a  glass-stop- 


CHAP,  ii  ILLUMINATING  GAS  275 

pered  cylinder  with  two  side  openings.  The  lower 
part  o  of  the  cylinder  is  filled  with  cellulose ;  upon 
this  lies  a  sheet  of  coarse  filter  paper,  and  above  that 
is  a  layer  of  bog-iron  ore,  mm. 

"  The  gas  enters  at  c  and  passes  out  through  p  into 
an  experimental  gas-meter,  and  then  into  the  aspira- 
tor. Before  beginning  the  experiment,  purified  illu- 
minating gas  is  allowed  to  pass  through  the  washing 
apparatus  for  ten  minutes  to  destroy  the  surface 
adhesion. 

"  The  cotton  in  B  should  not  be  at  all  brown  at  the 
end  of  the  experiment ;  if  it  is,  it  must  be  extracted 
with  carbon  disulphide. 

"  The  solution  thus  obtained  is  placed  in  a  weighed 
dish,  and  is  allowed  to  evaporate.  According  to 
Tieftrunk's  experience,  one-third  of  the  total  oil 
passes  off  at  the  same  time,  and  a  correction  is  made 
for  this  after  the  residue  has  been  weighed. 

"  When  the  experiment  is  ended,  the  apparatus  is 
taken  apart,  the  lid  of  the  vessel  A  is  raised,  the  tar 
adhering  to  the  bell  h  is  washed  down  with  the  aid 
of  a  wash-bottle  filled  with  alcohol  of  35°  Tr.,  and 
the  whole  is  allowed  to  stand  for  twelve  hours.  The 
solution  is  then  filtered  through  a  dried  and  weighed 
filter;  the  aspirator  is  used  in  this  operation,  but 
care  is  taken  to  turn  it  off  when,  toward  the  last,  the 
liquid  tar  is  brought  upon  the  filter.  After  wash- 
ing, the  filter  and  its  contents  are  placed  in  a  desic- 
cator, and  after  drying  for  twelve  hours  both  are 
weighed.  The  weighing  of  the  filter  with  and  with- 
out the  tar  may  conveniently  be  performed  in  a  glass 
dish  with  steep  sides.  Some  particles  of  tar  remain 
clinging  to  the  bell  and  the  walls  of  the  glass  cylinder, 


276  GAS  ANALYSIS  PART  m 

in  spite  of  the  washing.  As  this  cannot  be  avoided, 
the  amount  of  tar  adhering  to  the  glass  is  determined 
by  putting  the  apparatus  —  whose  original  weight 
must  be  known  —  together  again,  and  drawing  100 
liters  of  dry  air  through  it.  By  this  current  of  air, 
which  lasts  for  about  forty  minutes,  all  water  adher- 
ing to  the  walls  is  surely  driven  out,  and  the  increase 
of  weight  of  the  apparatus  gives  the  amount  of  the 
adhering  tar.  The  weighings  are  made  on  a  balance 
which,  with  a  load  of  1  kg.,  is  sensitive  to  0.01  g. 

"  Large  volumes  of  gas  are  required  in  determining 
the  tar  by  this  method.  Gases  which  contain  much 
tar,  and  which  are  often  still  warm,  are  first  passed 
through  a  long,  weighed  glass  tube  before  they  enter 
the  absorption  cylinder  A.  This  tube  slants  toward 
A  and  is  attached  to  <?,  and  in  it  a  sufficient  cooling 
and  condensation  of  the  tar  takes  place.  Most  of  the 
tar  passes  into  c  and  collects  at  the  bottom  of  A.  250 
liters  of  gas  are  passed  through  the  apparatus  with  a 
speed  of  from  30  to  40  liters  an  hour.  If  the  gas  to  be 
examined  has  already  passed  through  the  condenser, 
or,  in  other  words,  if  the  gas  sample  is  taken  either 
before  or  after  the  scrubbers,  500  liters  of  the  gas 
must  be  used,  and  it  may  be  given  a  speed  of  from 
50  to  60  liters  per  hour. 

"  Operating  in  this  manner,  Tieftrunk  found  in 
every  1000  cubic  meters,  of  gas  — 

Before  the  condensers  ...       150.0     to  200  kg.  tar 

"         "    scrubbers     .     .     .        25.0     »     75      " 
After  the  scrubbers  .     ...          0.5     "     20      " 

"These  figures  are  only  approximate.  They  vary 
greatly,  and  the  cause  of  these  variations  lies  in 


CHAP,  ii  ILLUMINATING   GAS  277 

the  character  of  the  coal,  the  method  of  distillation, 
the  form  of  the  condensers,  the  action  of  the  same,  the 
form  and  action  of  the  scrubbers,  the  size  of  the  ap- 
paratus, etc." 

Bunsen l  determines  the  gaseous  hydrocarbons  that 
are  not  properly  gases,  in  purified  illuminating  gas, 
by  slowly  passing  the  gas,  which  is  first  carefully 
dried  by  calcium  chloride,  through  a  long  glass  tube 
bent  slightly  upward  at  its  lower  end,  and  then 
through  a  series  of  wash-bottles,  the  tube  and  wash- 
bottles  being  filled  with  absolute  alcohol.  The  greater 
part  of  these  liquid  hydrocarbons  which  are  present 
in  the  gas  as  vapours  collect  in  the  tube ;  only  a  very 
small  amount  is  found  in  the  alcohol  of  the  last 
wash-bottle. 

If  the  alcoholic  contents  of  the  washing  apparatus 
be  poured  into  a  large  excess  of  a  concentrated  so- 
lution of  sodium  chloride,  the  liquid  hydrocarbons 
separate,  without  appreciable  evolution  of  gas,  as  a 
milky  cloud,  which,  upon  standing,  unites  to  a  clear 
and  colourless  oily  layer  upon  the  surface  of  the  salt 
solution.  Three  cubic  meters  of  the  Heidelberg 
illuminating  gas,  passed  through  1  liter  of  alcohol, 
yielded  a  liquid  which,  after  being  freed  from  alcohol 
by  washing  with  water  and  dried  over  calcium  chlor- 
ide, gave  36  g.  of  a  clear  liquid  having  the  odour 
of  pure  benzene.  This  liquid  began  to  boil  between 
80°  and  90°  C.,  and  the  boiling-point  rose  gradually 
to  140°  C.,  only  a  very  small  residue  boiling  at  a 
still  higher  temperature.  By  a  number  of  fractional 
distillations  the  larger  part  of  the  total  liquid  was 
obtained  as  a  product  which  boiled  between  90°  and 

1  Bunsen,  Gasometrische  Methoden,  2d  ed.,  p.  144. 


278  GAS   ANALYSIS  PART  in 

100°  C.,  and  which  upon  being  cooled  to  below  0°  C. 
separated  almost  completely  as  pure  benzene. 

The  hydrocarbons  taken  up  by  alcohol  consisted 
chiefly  of  benzene.  The  hydrocarbons  mixed  with 
the  benzene  constituted  so  small  a  portion  of  the 
whole  that  their  amounts  could  be  wholly  dis- 
regarded in  the  analysis  as  lying  within  the  limits 
of  experimental  error. 

In  all  of  the  illuminating  gases,  coming  from  the 
most  varied  sources,  which  Bunsen  had  opportunity 
to  examine,  not  one  contained  less  than  from  4  to 
12  times  as  much  gas  absorbable  by  sulphuric  acid 
as  there  was  benzene  present.  Hence  that  portion 
of  illuminating  gas  which  gives  the  lighting  power 
consists  chiefly  of  gaseous  hydrocarbons. 

The  gases  absorbable  by  sulphuric  acid  consist 
essentially  of  ethylene,  propylene,  and  benzene 
vapours.  All  other  hydrocarbons  are  here  present 
in  such  small  quantities  that  for  analytical  purposes 
they  need  not  be  considered. 

If  a  more  exhaustive  analysis  is  to  be  made, 
we  must  examine,  in  addition  to  those  hydrocarbons 
absorbable  by  alcohol,  those  products  also  which 
result  from  leading  large  amounts  of  the  gas  through 
sulphuric  acid,  the  products  formed  by  the  action  of 
chlorine  and  bromine,  the  constituents  separable  by 
ammonium  cuprous  chloride,  and  finally,  if  possible, 
the  condensation  products  which  separate  out  when 
the  gas  is  compressed. 

E.  St.  Claire-Deville l  has  made  a  large  number  of 
determinations  of  these  hydrocarbon  vapours  by  sepa- 
rating them  through  cooling  to  -22°C.  We  have 

1  Journal  des  usines  a  Gaz,  1889,  13. 


CHAP,  ii  ILLUMINATING   GAS  279 

tested  this  method  and  also  that  proposed  by  Bunsen 
(p.  277),  and  have  obtained  the  following  results:1  — 

1427  liters  of  illuminating  gas  gave  by  Bunsen's 
method  15.4  ccm.  of  liquid  hydrocarbons,  from 
which,  by  fractional  distillation  and  freezing,  3.5 
ccm.  of  benzene  was  obtained. 

1497  liters  of  illuminating  gas  gave  by  Deville's 
method  13  ccm.  of  liquid  hydrocarbons,  containing 
5  ccm.  benzene. 

That  the  results  by  the  two  methods  did  not 
agree  better  is  to  be  explained  by  the  fact  that  it 
is  almost  impossible  to  keep  the  temperature  con- 
stant at  —  22°  C.  The  experiments  were  made  under 
the  most  favourable  external  conditions,  i.e.  during 
very  cold  days  in  winter,  but  in  spite  of  the  greatest 
care  it  was  impossible  to  avoid  considerable  varia- 
tions of  temperature.  More  of  the  hydrocarbons 
were  obtained  by  Bunsen's  method  than  by  that  of 
Deville. 

Further  investigation  showed  that  it  is  possible 
with  1  ccm.  of  alcohol  to  absorb  and  volumetri- 
cally  determine  the  hydrocarbon  vapour  present  in 
100  ccm.  of  illuminating  gas.  In  carrying  out  this 
determination,  a  sample  of  illuminating  gas  is  meas- 
ured over  water  which  has  been  saturated  with  the 
gas.  The  burette  is  then  connected  with  the  mercury 
pipette  of  the  form  shown  in  Fig.  37,  which  contains 
above  the  mercury  1  ccm.  of  absolute  alcohol.  To 
avoid  the  absorption  by  the  alcohol  of  gases  other 
than  these  hydrocarbon  vapours,  it  is  well  to  first 
saturate  the  alcohol  with  the  illuminating  gas  by 

1  Hempel  and  Dennis,  Bericfite  der  deutschen  chemischen  Ge- 
sellschaft,  24,  1162. 


280  GAS   ANALYSIS  PART  in 

drawing  over  about  100  ccm.  of  the  gas  into  the 
pipette  and  then  driving  it  out  again.  The  satura- 
tion of  the  alcohol  with  the  gas  and  the  absorption 
of  the  hydrocarbon  vapours  by  the  alcohol  are  com- 
pletely effected  by  simply  passing  the  gas  into  the 
pipette  and  driving  it  out.  The  entrance  of  water 
into  the  pipette  and  the  consequent  dilution  of  the 
alcohol  should  be  carefully  avoided,  because  dilute 
alcohol  does  not  completely  absorb  the  vapours.  The 
entrance  of  alcohol  into  the  piece  of  rubber  tubing 
attached  to  the  capillary  of  the  burette  must  also  be 
avoided,  for  if  alcohol  should  enter  the  burette,  its 
tension  would  cause  an  appreciable  error. 

If  a  high  degree  of  accuracy  is  desired,  it  is  best 
to  transfer  the  gas,  after  the  absorption  with  alcohol 
and  before  measuring,  into  a  second  mercury  pipette 
which  contains  1  ccm.  of  water  and  to  shake  the 
gas  for  some  minutes  in  this  pipette.  On  trans- 
ferring the  gas  again  into  the  burette,  the  diminu- 
tion in  volume  will  accurately  give  the  amount  of 
hydrocarbon  vapours  present  in  the  illuminating 
gas. 

100  ccm.  of  Dresden  illuminating  gas  when  ana- 
lysed with  a  burette  filled  with  mercury  and  affording 
correction  for  temperature  and  pressure  gave  in  two 
experiments  — 

0.74  per  cent  of  hydrocarbon  vapours 
0.70        "         "  "  " 

To  prepare  a  gas  containing  a  known  amount  of 
hydrocarbon  vapours,  90  ccm.  of  the  above  gas  was 
shaken  for  a  short  time  with  benzene  contained  in  a 
gas  pipette.  The  volume  was  hereby  increased  to 


CHAP,  ii  ILLUMINATING   GAS  281 

93.1  ccm.  After  the  absorption  of  the  hydrocarbon 
vapours,  the  residue  was  89.4  ccm. 

In  a  second  experiment,  90  ccm.  of  the  gas  shaken 
with  benzene  increased  to  93.0  ccm.  After  the  ab- 
sorption the  volume  was  89.4  ccm. 

These  experiments  show  that  with  1  ccm.  of  alco- 
hol and  1  ccm.  of  water  it  is  possible  to  quantita- 
tively absorb  the  hydrocarbon  vapours  from  a  gas 
which  contains  about  3  per  cent  of  these  vapours. 

The  same  gas  as  was  used  in  the  above  experi- 
ments was  analysed  with  the  aid  of  a  burette  filled 
with  water,  but  with  the  other  details'  of  the  analy- 
sis exactly  as  above  described,  and  the  two  results 
for  the  hydrocarbon  vapours  were  0.5  per  cent  and 
0.63  per  cent. 

A  sample  of  oil  gas  analysed  in  this  manner  gave 
4.6  per  cent  of  hydrocarbon  vapours. 

Since  these  vapours  are  quite  soluble  in  potassium 
hydroxide,  their  determination  must  precede  those 
of  the  other  constituents  of  the  gas.  Otherwise  the 
results  for  carbon  dioxide  will  be  too  high,  and 
those  for  the  heavy  hydrocarbons  too  low. 

To  determine  the  amount  of  benzene  in  a  gas 
mixture,  Harbeck  and  Lunge 1  led  a  large  amount  of 
the  gas  through  an  absorption  apparatus  which  con- 
tained a  mixture  of  concentrated  nitric  acid  and  sul- 
phuric acid.  Dinitrobenzene  is  formed,  and,  after 
dilution  with  water,  it  can  be  separated  from  the 
other  substance  by  shaking  with  ether.  It  has  been 
found  that  the  substances  formed  by  the  action  of 
ethylene  and  other  gases  and  vapours  upon  the 

1  E.  Harbeck  and  G.  Lunge,  Zeitschrift  fur  anorganische  Che* 
mie,  16,  41. 


282  GAS  ANALYSIS  PART  in 

above-mentioned  concentrated  acids  are  easily  solu- 
ble in  water,  and  cannot  be  extracted  with  ether 
from  an  aqueous  solution. 

4.    The  Volumetric  Analysis 

For  the  volumetric  analysis,  a  sufficient  quantity 
of  water  must  first  be  saturated  with  the  illuminat- 
ing gas,  as  directed  on  p.  53.  The  same  must  be 
done  with  the  caustic  potash  pipette,  unless  a  double 
pipette  for  solid  and  liquid  reagents,  which  is  filled 
with  illuminating  gas,  is  being  used. 

The  hydrocarbon  vapours  are  first  absorbed  witl\ 
alcohol,  then  carbon  dioxide  with  potassium  hydrox- 
ide, then  the  heavy  hydrocarbons  with  fuming  sul- 
phuric acid,  then  oxygen  with  phosphorus,  and 
lastly  carbon  monoxide  with  the  ammoniacal  cuprous 
chloride  solution.  The  residue,  which  consists  of 
methane,  hydrogen,  and  nitrogen,  is  measured,  and 
is  then  led  back  into  the  cuprous  chloride  pipette, 
and  a  portion  is  taken  for  the  explosion  analysis. 

With  ordinary  illuminating  gas  12  ccm.  of  the  resi- 
due suffice  for  the  explosion. 

These  12  ccm.  are  measured  off  in  the  gas  burette, 
and  enough  air  is  drawn  in  to  bring  the  mixture  to 
about  100  ccm.  In  all  these  measurements  the  run- 
ning down  of  the  liquid  must  be  most  carefully 
waited  for,  because  the  amount  of  gas  taken  is  so 
small  that  any  errors  that  may  be  made  are  greatly 
multiplied. 

The  gas  mixture  is  now  burned  in  the  explosion 
pipette.  The  gas  is  then  transferred  to  the  burette 
and  the  total  contraction  is  measured.  Then  the 


CHAP,  ii  ILLUMINATING  GAS  283 

carbon  dioxide  is  absorbed  with  potassium  hydrox- 
ide, and  finally  the  oxygen  in  excess  is  absorbed 
with  phosphorus.  The  last  determination  is  made 
merely  to  be  sure  that  a  sufficient  excess  of  oxygen 
was  present  in  the  combustion. 

An  analysis  of  illuminating  gas  is  here  given  for 
the  sake  of  illustration. 

100  ccm.  of  illuminating  gas  measured  off  (see  p. 
37). 

Shaken  with  alcohol  and  then  with  water,  as  de- 
scribed on  p.  279  ;  drawn  back  into  the  burette  and 
measured  at  the  end  of  three  minutes  (time  allowed 
for  the  running  down). 

0.7  ccm.  or  per  cent  hydrocarbon  vapours. 

Passed  into  caustic  potash  pipette  and  drawn 
directly  back  into  the  burette  ;  measured  after  three 
minutes.  Measurement  gave  4.1  ccm. ;  hence  there 
was  present  4.1  —  0.7  =  3.4  ccm.  or  per  cent  carbon 
dioxide. 

Burette  now  connected  by  means  of  a  dry  piece  of 
rubber  tube  and  a  dry  capillary  with  the  pipette  con- 
taining fuming  sulphuric  acid.  Gas  driven  over 
and  drawn  back  at  once  into  the  burette.  Gas  now 
passed  again  into  caustic  potash  pipette,  and  after 
being  drawn  back  into  the  burette  and  allowed  to 
stand  three  minutes,  again  measured.  The  measure- 
ment gave  8.4  ccm.;  hence  there  were  8.4  —  4.1 
==4.3  ccm.  or  4.3  per  cent  of  heavy  hydrocarbons 
present. 

The  gas  now  passed  into  phosphorus  pipette  and  al- 
lowed to  remain  for  three  minutes ;  then  drawn  back 
into  burette  and  measured  at  the  end  of  three  minutes. 
Reading  gave  8.4  ccm. ;  hence  no  oxygen  was  present. 


284  GAS   ANALYSIS  PART  in 

The  gas  was  then  passed  into  the  pipette  contain- 
ing' ammoniacal  cuprous  chloride  which  had  been 
repeatedly  used,  and  was  shaken  therein  for  two 
minutes.  It  was  then  drawn  back  into  the  burette 
and  transferred  at  once  to  a  second  pipette  contain- 
ing ammoniacal  cuprous  chloride  which  had  been 
used  but  little,  and  it  was  here  shaken  for  three  min- 
utes. Drawn  back  into  the  burette  and  measured 
after  three  minutes  ;  the  reading  was  18  ccm. ;  hence 
there  was  18  ccm.  —  8.4  =  9.6  ccm.  or  per  cent  car- 
bon monoxide  present. 

The  remaining  82  ccm.  of  gas  was  then  passed 
back  into  the  cuprous  chloride  pipette,  and  the 
pipette  was  closed  with  an  ordinary  pinchcock. 

The  water  in  the  burette  is  poured  out,  the  bu- 
rette washed  with  hydrochloric  acid  and  then  with 
distilled  water,  and  then  filled  with  water  which  is 
saturated  not  with  illuminating  gas,  but  with  air. 

12  to  15  ccm.  of  the  gas  residue  is  now  measured 
off  into  the  burette.  In  this  case  13.2  ccm.  was 
taken. 

So  much  air  is  then  drawn  in  that  the  total  vol- 
ume of  the  gas  residue  taken  and  the  air  amounts  to 
about  100  ccm.  In  this  case  it  was  99.6  ccm. 

This  mixture  is  now  brought  into  an  explosion 
pipette  filled  with  mercury,  care  being  taken  that 
the  capillary  remains  full  of  water.  The  rubber  con- 
necting piece  is  closed  by  a  strong  pinchcock,  and  a 
piece  of  glass  rod  is  slipped  into  the  end  of  the  rub- 
ber tube.  The  pipette  is  then  vigorously  shaken, 
the  glass  stopcock  is  closed,  the  pipette  is  connected 
with  the  poles  of  an  induction  coil,  and  by  lowering 
the  dip  battery  the  mixture  is  exploded.  The  glass 


CHAP,  ii  ILLUMINATING   GAS  286 

stopcock  is  at  once  opened  and  the  remaining  gas  is 
transferred  without  delay  to  the  burette,  and,  after 
three  minutes,  measured.  The  result  here  was 
78  ccm. 

The  total  contraction  was  therefore  99.6  —  78  = 
21.6  ccm. 

The  gas  remaining  from  the  combustion  is  now 
passed  into  the  caustic  potash  pipette,  drawn  di- 
rectly back  into  the  burette,  and,  after  three  min- 
utes, measured.  The  reading  was  73.2  ccm.  Hence 
by  the  combustion  78  —  73.2  =  4.8  ccm.  of  carbon 
dioxide  was  formed. 

Although  this  gave  all  the  data  necessary  for  the 
calculation  of  the  analysis,  the  remaining  gas  was 
nevertheless  passed  into  the  phosphorus  pipette  in 
order  to  be  sure  that  an  excess  of  oxygen  was  pres- 
ent in  the  combustion,  or,  in  other  words,  that  the 
gas  was  completely  burned.  The  measurement  gave 
70.2  ccm. 

Hence  there  was  73.2  —  70.2  =  3  ccm.  of  oxygen 
in  excess. 

In  the  combustion  of  the  marsh-gas  its  own  vol- 
ume of  carbon  dioxide  is  formed,  so  that  in  the 
13.2  ccm.  of  the  gas  residue  taken  for  the  explosion 
there  were  4.8  ccm.  of  marsh-gas. 

The  marsh-gas  in  the  total  gas  residue  of  82  ccm. 
is  found  by  the  proportion  — 

13.2:  82  =  4.8:  z, 

x=  29.8  per  cent  marsh-gas. 

Since  marsh-gas  in  burning  unites  with  twice  its 
volume  of  oxygen,  the  contraction  which  has  re- 
sulted from  the  combustion  of  the  hydrogen  is 


286  GAS  ANALYSIS  PART  in 

found  by  subtracting  twice  the  volume  of  the  car- 
bon dioxide  found  from  the  total  contraction. 
21.6  — (2  x  4.8)  =  12  ccm.  contraction  due  to  the 
burning  of  hydrogen. 

One  volume  of  hydrogen  unites,  in  burning,  with 
one-half  its  volume  of  oxygen ;  hence  the  volume  of 
the  hydrogen  is  found  by  multiplying  12  by  J.  Thus 
the  13.2  ccm.  of  the  gas  residue  taken  for  the  ex- 
plosion contained  8  ccm.  of  hydrogen.  The  total 
amount  of  hydrogen  is  given  by  the  proportion  — 

13.2  :  82  =  8  :  x, 

x  —  49.6  per  cent  hydrogen. 

The  nitrogen  is  found  by  subtracting  the  sum  of 
all  the  other  constituents  from  100.  This  gives  2.6 
per  cent. 

Hence  the  illuminating  gas  contained  — 

0.7  per  cent  hydrocarbon  vapours 

3.4  "  carbon  dioxide 

4.3  "  heavy  hydrocarbons 

0.0  "  oxygen 

9.6  "  carbon  monoxide 

29.8  "  methane 

49.6  "  hydrogen 

2.6  "  nitrogen. 


100.0 


In  this  analysis  the  following  apparatus  was  used :  — 
One  gas  burette  (Fig.  27,  p.  35). 
A  mercury  pipette  (Fig.  37,  p.  67). 
One  gas  pipette  for  fuming  sulphuric  acid  (Fig.  82, 
p.  229). 


CHAP,  ii  ILLUMINATING   GAS  287 

Two  double  absorption  pipettes  for  cuprous  chlor- 
ide (Fig.  33,  p.  51). 

A  gas  pipette  for  phosphorus  (Fig.  32,  p.  49). 

An  explosion  pipette  (Fig.  63,  p.  130). 

A  small  induction  coil  (Fig.  69,  p.  137). 

A  dip  battery  (Fig.  68,  p.  135). 

A  number  of  capillary  connecting  tubes. 

A  three-minute  sand  glass. 

In  place  of  the  absorption  pipette  there  may  be 
used  either  a  Winkler-Dennis  combustion  pipette 
(Fig.  70,  p.  138)  or  a  Drehschmidt  platinum  capil- 
lary (Fig.  71,  p.  140). 

With  careful  work,  the  determinations  of  the  hy- 
drocarbon vapours,  carbon  dioxide,  heavy  hydrocar- 
bons, oxygen,  and  carbon  monoxide  are  exact  to  about 
0.2  per  cent,  but  the  experimental  errors  in  the  analy- 
sis of  the  marsh-gas,  hydrogen,  and  nitrogen  may  rise 
to  1  per  cent.  The  reason  for  this  lies  in  the  fact 
that  only  small  quantities  of  gas  can  be  taken  for  the 
explosion,  and  that  all  results  are  then  calculated  for 
a  gas  volume  about  six  times  as  large.  In  the  above 
example  the  proportion  was  13.2  :  82. 

It  would  be  unadvisable,  and  would  also  lead  to 
no  greater  accuracy,  to  explode  very  large  volumes, 
because  the  error  caused  by  the  unequal  heating  of  the 
gas  mixture  increases  as  the  quantity  of  gas  increases. 

Direct  comparison  of  two  analyses,  one  of  which 
was  made  entirely  over  mercury,  while  the  other  was 
carried  out  in  a  burette  filled  with  water  and  an  ex- 
plosion pipette  filled  with  mercury  in  the  manner 
just  described,  showed  that  the  determination  of 
carbon  dioxide  by  the  latter  method  was  quite  exact. 

As  it  was  suspected  that  the  residue  of  marsh-gas, 


288  GAS  ANALYSIS  PART  in 

hydrogen,  and  nitrogen  might  contain,  in  addition  to 
these  gases,  higher  members  of  the  marsh-gas  series, 
experiments  were  made  to  answer  the  question. 

Mercury  was  employed  as  confining  liquid  and  the 
greatest  care  was  used.  The  result  showed  that  when 
the  hydrogen  had  first  been  absorbed  by  palladium,  the 
carbon  dioxide  formed  in  the  explosion  corresponded 
exactly  to  the  oxygen  used  and  the  contraction  ob- 
served. We  may  hence  conclude  that  in  ordinary 
illuminating  gas  there  is  no  appreciable  amount  of 
ethane  present  with  the  methane. 

The  determination  of  hydrogen  may  be  made  more 
exactly  by  absorption  with  palladium  (see  p.  181). 
Yet  many  experiments  have  shown  that  the  accuracy 
attained  by  making  use  of  the  fractional  combustion  of 
hydrogen  is  not  greater  than  in  the  above  procedure. 

The  following  analysis  is  given  to  illustrate  the 
calculation  of  the  analysis  when  the  hydrogen  is 
fractionally  burned. 

The  direct  absorption  gave  — 

0.6  per  cent  hydrocarbon  vapours 
3.4        "        carbon  dioxide 
4.4        "         heavy  hydrocarbons 
0.3        "        oxygen 
10.1        "        carbon  monoxide. 

The  residue  of  hydrogen,  methane,  and ,  nitrogen 
amounted  to  81.2  ccm.  This  was  transferred  to  a 
pipette  and  40.5  ccm.  were  measured  off  in  a  burette 
for  the  fractional  combustion  of  the  hydrogen.  To 
this  was  added  air  —  in  this  case  58.7  ccm.  — and  the 
mixture  was  passed  into  a  pipette  filled  with  water. 
Then  more  air  was  measured  off  in  the  burette  and 


CHAP,  ii  ILLUMINATING   GAS  289 

transferred  to  the  pipette,  so  that  the  total  amount 
of  air  added  would  without  doubt  be  sufficient  for 
the  combustion  of  the  hydrogen.  In  this  second 
measurement  16.1  ccm.  of  air  were  taken,  so  that 
the  total  amount  of  gas  taken  for  the  fractional  com- 
bustion was  — 

40.5  +  58.7  +  16.1  =  115.3  ccm. 

The  gases  were  vigorously  shaken  in  the  pipette 
to  thoroughly  mix  them,  and  were  then  fractionally 
burned  by  leading  them  over  0.5  g.  of  palladium. 

The  volume  after  the  combustion  was  81  ccm.  ; 
hence  the  contraction  was  — 

115.3  -  81  =  34.3  ccm., 

corresponding  to  22.9  ccm.  of  hydrogen,  the  total 
amount  of  hydrogen  being  found  by  the  proportion — 

40.5  :  81.2  =  22.9  :  x, 

x  =  45.9  per  cent  hydrogen. 

To  determine  the  methane,  19.9  ccm.  of  the  residue 
of  hydrogen,  methane,  and  nitrogen  were  taken  and, 
together  with  110  ccm.  of  air,  were  transferred  to  the 
explosion  pipette.  The  gases  were  well  mixed,  and 
were  then  exploded,  freed  from  carbon  dioxide  in  the 
potassium  hydroxide  pipette,  and  measured.  There 
remained  90.5  ccm.  The  contraction  was  — 

110  +  19.9  -  90.5  =  39.4  ccm. 

From  the  determination  of  the  hydrogen  by  the 

fractional  combustion  we  know  that  in  19.9  ccm.  of 

the  residue,  by  hydrogen  would  cause  a  contraction 

of  16.9  ccm.  (40.5  : 19.9  =  34.3  :  x,  x  =  16.9);  hence 

u 


290  GAS  ANALYSIS  PART  m 

the  contraction  due  to  the  methane  is  equal  to  39.4 
—  16.9  =  22.5  ccm.,  and  the  volume  of  the  methane 
itself  is  7.5  ccm. 

The  per  cent  of  methane  is  — 

19.9  :  81.2  =  7.5  :  z, 

x  =  30.6  per  cent  marsh-gas. 

The  nitrogen  determined  by  difference  as  before  is 
4.7  per  cent,  so  that  the  composition  of  the  gas  was 
as  follows :  — 

0.6  per  cent  hydrocarbon  vapours 

3.4  "  carbon  dioxide 

4.4  "  heavy  hydrocarbons 

0.3  "  oxygen 

10.1  "  carbon  monoxide 

45.9  "  hydrogen 

30.6  "  marsh-gas 

4.7  "  nitrogen. 

EXAMPLE  TO  ILLUSTATE  THE  METHOD  OF  PROCED- 
URE AND  THE  CALCULATION  IN  THE  ANALYSIS 
OF  GENERATOR  GAS 

In  addition  to  the  apparatus  used  for  the  analysis 
of  illuminating  gas,  a  hydrogen  pipette  (p.  131)  is 
here  necessary,  provided  a  Winkler-Dennis  combus-. 
tion  pipette  or  a  Drehschmidt  platinum  capillary  is 
not  used. 

The  manipulation  differs  merely  as  concerns  the 
combustion  of  the  unabsorbable  residue. 

A  generator  gas  made  from  brown  coal  in  a  shaft 
generator  gave  — 


CHAP,  ii  ILLUMINATING   GAS  291 

3.4  per  cent  carbon  dioxide 
0.8        "        heavy  hydrocarbons 
0.3        "        oxygen 
25.4        "        carbon  monoxide. 

The  residue  of  marsh-gas,  hydrogen,  and  nitrogen 
amounted  to  70.1  ccm.  The  gas  mixed  with  air 
would  not  explode,  hence  hydrogen  was  added. 

The  mixture  that  was  exploded  consisted  of  — 

15.3  ccm.  of  the  gas  residue 

84.0     "      air 

10.5     "      hydrogen. 

After  the  explosion  the  volume  was  — 

89.2  ccm., 
and  the  contraction  was  — 

(15.3  +  84  +  10.5)  -  89.2  =  20.6  ccm. 

The  10.5  ccm.  of  hydrogen  added,  used  up  in  its 
combustion  5.25  ccm.  of  oxygen,  so  that  15.75  ccm. 
must  be  subtracted  from  the  total  contraction  to 
ascertain  the  contraction  resulting  from  the  hydrogen 
and  marsh-gas  in  the  generator  gas. 

This  gives  4.85  ccm.  contraction. 

The  absorption  of  the  carbon  dioxide  formed  in 
the  combustion  gave  1.3  ccm. 

Since  this  volume  is  equal  to  that  of  the  meth- 
ane, the  following  proportion  gives  the  per  cent 
of  the  latter :  — 

15.3  ;  70.1=1. 3  :x, 

x  =  5.3  per  cent  marsh-gas. 

The  marsh-gas  unites  with  twice  its  volume  of 
oxygen,  so  that  the  contraction  resulting  from  the 


292  GAS   ANALYSIS  PART  in 

combustion  of  the  hydrogen  is  found  by  subtracting 
twice  the  volume  of  the  carbon  dioxide  formed  from 
the  total  contraction  — 

4.85 -(2x1. 3)  =  2.25  ccm. 

Hence  the  15.3  ccm.  of  the  gas  residue  taken  for 
the  explosion  contained  — 

2.25  x  §  =  1.5  ccm.  hydrogen, 
and  the  total  amount  of  hydrogen  is  — 

15.3:  70.1  =  1.5  :z, 

x=  6.8  ccm.  or  per  cent  hydrogen. 

The  nitrogen,  by  difference,  was  57.4  per  cent. 
Hence  the  generator  gas  contained  — 

3.4  per  cent  carbon  dioxide 

0.8  "  heavy  hydrocarbons 

0.3  "  oxygen 

25.4  "  carbon  monoxide 

5.9  "  marsh-gas 

6.8  "  hydrogen 

57.4  "  nitrogen. 

Berthelot's  method  for  the  analysis  of  illuminating 
gas,  in  which  the  heavy  hydrocarbons  are  separated 
from  benzene  by  bromine,  and  the  benzene  then 
absorbed  by  fuming  nitric  acid,  has  been  found  by 
F.  P.  Treadwell  and  H.  N.  Stokes 1  to  be  impracti- 
cable. On  the  one  hand,  bromine  absorbs  some  ben- 
zene in  addition  to  the  ethylene,  and,  on  the  other 
hand,  fuming  nitric  acid  oxidises  carbon  monoxide. 

1  Berichte  der  deutschen  chemischen  Gesellschaft,  21,  3131. 


CHAP,  ii  ILLUMINATING   GAS  293 

They  found  it  possible  to  completely  oxidise  carbon 
monoxide  by  shaking  the  gas  for  a  long  time  with 
fuming  nitric  acid. 

At  the  present  time  there  exists  no  simple  method 
for  the  separation  of  the  heavy  hydrocarbons. 

The  accuracy  of  the  combustion  analysis  for  the 
determination  of  hydrogen  and  methane  may  be 
greatly  increased  by  the  use  of  the  method  of  Dennis 
and  Hopkins.1  This  procedure  permits  of  the  use  of 
large  volumes  of  gas,  and  effects  the  combustion  by 
means  of  pure  oxygen,  thus  avoiding  to  a  great 
degree  the  possibility  of  the  formation  of  oxides  of 
nitrogen.  The  combustion  pipette  employed  is  that 
described  on  p.  138,  Fig.  70.  A  measured  quan- 
tity of  the  gas  to  be  burned  is  introduced  into  this 
pipette,  and  there  is  measured  off  in  the  gas  burette 
a  quantity  of  oxygen  more  than  sufficient  to  com- 
pletely burn  the  gas.  The  burette  is  then  connected 
with  the  pipette  by  the  usual  bent  capillary  tube 
(see  Fig.  91),  and  the  level-bulb  of  the  pipette  and  the 
level-tube  of  the  burette  are  placed  at  such  heights 
that  the  gases  in  both  pipette  and  burette  are  approx- 
imately under  atmospheric  pressure.  A  screw  pinch- 
cock  k  which  has  previously  been  placed  upon  the 
rubber  tube  joining  the  burette  with  its  level-tube  is 
now  tightly  screwed  down  so  as  to  prevent,  for  the 
present,  any  movement  of  the  mercury  in  the  burette. 
The  level-tube  is  now  placed  at  such  a  height  that 
when  the  screw  pinchcock  k  is  opened  the  mercury 
will  rise  to  the  top  of  the  burette  but  will  not  pass 
over  into  the  pipette.  The  pinchcocks  0,  o  on  the 

1  J.  Am.  Chem.  Soc.,  21,  398;  Zeitschr.  f.  Anorgan.   Chemie, 
19,  179. 


294 


GAS  ANALYSIS 


PART  III 


connections   between   the   burette   and    pipette   are 
now  opened,  and  the  electric  current,  which  should 


FIG.  91. 


be  just  strong  enough  to  maintain  the  spiral  at  a 
red  heat,  is  turned  on.  Any  electrical  apparatus 
furnishing  a  current  of  sufficient  strength  to  heat 


CHAP,  ii  ILLUMINATING  GAS  295 

the  platinum  spiral  to  redness  may,  of  course,  be 
employed.  If  the  current  from  a  dynamo  or  storage 
battery  is  at  the  operator's  disposal,  the  arrangement 
shown  in  Fig.  91  can  be  recommended  as  being  both 
simple  and  convenient.  The  current  is  passed 
through  the  resistance  frame  F.  (A  small  frame 
carrying  German  silver  wire  about  1.5  mm.  in 
diameter  maybe  used.)  The  terminals  on  the  com- 
bustion pipette  are  connected  with  the  frame  by 
means  of  the  flexible  wires  V  and  W,  the  ends  of 
these  wires  being  simply  hooked  into  the  coiled  wire 
of  the  frame.  The  current  passing  through  the 
platinum  spiral  can  then  be  varied  at  will  by  simply 
hooking  the  end  of  W  into  the  resistance  coil  at  a 
greater  or  less  distance  from  V.  Instead  of  con- 
necting V  and  W  directly  with  the  resistance  frame 
in  the  manner  described,  it  will  be  found  con- 
venient to  introduce  into  the  circuit  the  rheostat 
R.  This  will  enable  the  operator  to  control  easily 
and  instantly  the  current  flowing  through  the  plati- 
num spiral. 

When  the  spiral  has  been  brought  to  the  proper 
temperature  the  screw  pinchcock  k  is  carefully 
opened  and  a  slow  and  steady  current  of  oxygen  is 
passed  over  into  the  pipette.  From  10  to  20  ccm. 
of  oxygen  per  minute  may  be  introduced,  but  the 
amount  is,  of  course,  somewhat  dependent  upon  the 
length  and  temperature  of  the  spiral.  The  combus- 
tion takes  place  quietly  without  the  appearance  of  a 
flame,  and  if  the  operation  is  properly  conducted 
there  is  no  possibility  of  an  explosion,  since  the  com- 
bustible gas  and  the  oxygen  are  in  separate  vessels 
and  are  made  to  combine  as  fast  as  they  mix. 


296  GAS   ANALYSIS  PART  in 

Nevertheless,  a  screen  of  heavy  glass  is  always  placed 
between  the  pipette  and  the  operator  to  insure  pro- 
tection for  the  face  in  case  of  possible  accident. 
This  precaution  should  be  invariably  taken  in  all 
combustion  or  explosion  analyses  of  gas  mixtures. 
After  the  oxygen  has  been  passed  into  the  pipette, 
the  spiral  is  kept  at  a  red  heat  for  about  one  minute 
to  insure  complete  combustion  of  the  gas.  When, 
however,  hydrogen  alone  is  being  burned,  the  com- 
bustion is  complete  almost  as  soon  as  sufficient  oxygen 
has  been  introduced.  When  the  combustion  is  fin- 
ished, the  residual  gas  is  passed  back  into  the  burette 
and  measured. 

The  volume  of  gas  which  may  be  taken  for  the 
combustion  is  limited  only  by  the  capacity  of  the 
measuring  burette,  but  for  convenience  in  handling 
neither  the  combustible  gas,  the  oxygen  required, 
nor  the  residue  after  combustion  is  allowed  to  exceed 
100  ccm.  The  volume  of  gas  in  the  pipette  at  any 
time  during  the  combustion  should  be  sufficient  to 
prevent  the  mercury  from  rising  and  covering  the 
spiral,  or  short-circuiting  the  current.  This  would 
take  place  if  pure  hydrogen  were  burned  by  add- 
ing pure  oxygen,  but  the  difficulty  in  this  case  is 
avoided  by  introducing  into  the  100  ccm.  of  hydro- 
gen about  95  ccm.  of  a  mixture  of  equal  parts  of 
oxygen  and  air. 

The  results  obtained  in  the  determination  of  hy- 
drogen by  this  method  have  already  been  given  on 
p.  177. 

Experiments  have  also  been  made  upon  the  simul- 
taneous combustion  and  determination  of  hydrogen 
and  methane  in  illuminating  gas. 


CHAP.  II 


ILLUMINATING   GAS 


297 


Illuminating  gas  was  passed  into  fuming  sulphuric 
acid  to  remove  hydrocarbon  vapors  and  heavy  hydro- 
carbons, then  shaken  with  alkaline  pyrogallol  to 
remove  oxygen,  carbon  dioxide,  and  the  fumes  of 
the  sulphuric  acid,  and  finally  shaken,  first  with  old 
and  then  with  fresh  cuprous  chloride,  to  remove 


I 

II 

in 

IV 

v 

Gas  residue  taken 
Oxygen  taken   .... 
Total        .... 

ccm. 

61.4 

98.5 
159.9 

ccm. 

64.50 
96.55 
161.05 

ccm. 

67.00 
98.55 
165.55 

ccm. 

64.0 
97.6 
161  6 

ccm. 

65.7 
100.0 
165  7 

Residue  after  combustion 
Contraction  

58.8 

101   1 

54.95 

10fi  10 

55.30 
110  9^ 

56.3 

inpL  q 

57.6 

1AQ    1 

Residue  after  absorbing 
CO2  in  KOH  pipette    . 
Carbon  dioxide  found     . 

Hydrogen     

34.3 
24.5 

Per  cent 

56  4 

29.15 
25.80 

Per  cent 

56.30 

28.60 
26.70 

Per  cent 
5660 

30.7 
25.6 

Per  cent 

56  4 

31.4 

26.2 

Percent 
56  5 

IVIethane 

39.9 

40.00 

3990 

40  0 

39  9 

Nitrogen  (diff.)     .     .     . 

3.7 

3.70 

3.50 

3.6 

3.6 

carbon  monoxide.  Measured  portions  of  the  residue 
which  now  contained  hydrogen,  methane,  and  nitrogen 
were  then  introduced  into  the  combustion  pipette  and 
burned  with  oxygen  in  the  manner  described  above. 
It  is  also  possible  to  determine  the  three  gases  — 
carbon  monoxide,  hydrogen,  and  methane  —  by  one 
combustion. 

A  mixture  of  these  gases  together  with  nitrogen 
was  obtained  by  extracting  from  illuminating  gas 
by  means  of  the  usual  absorbents  only  the  hydro- 
carbon vapours,  heavy  hydrocarbons,  oxygen,  and 


298  GAS   ANALYSIS  PART  m 

carbon  dioxide.  A  measured  volume  of  the  residue 
was  transferred  to  the  combustion  pipette  and  burned 
with  oxygen.  The  residual  gas  was  then  passed  back 
into  the  burette,  measured  to  ascertain  the  contrac- 
tion, and  then  passed  into  the  caustic  potash  pipette 
to  absorb  the  carbon  dioxide,  and  again  drawn  back 
and  measured.  In  the  meantime  a  known  volume 
of  hydrogen  had  been  brought  into  the  combustion 
pipette.  This  was  then  connected  with  the  burette 
which  now  contained  nitrogen  and  the  unconsumed 
oxygen,  the  current  was  turned  on,  and  the  oxygen 
was  passed  over  into  the  hydrogen.  From  the  re- 
sulting contraction  the  excess  of  oxygen  was  ascer- 
tained, and  the  difference  between  this  and  the 
oxygen  first  taken  gives  the  amount  of  oxygen  con- 
sumed in  the  combustion  of  the  carbon  monoxide, 
hydrogen,  and  methane. 

Having  thus  ascertained  the  contraction  resulting 
from  the  combustion,  the  volume  of  carbon  dioxide 
formed,  and  the  amount  of  oxygen  consumed,  we 
have  all  the  data  necessary  for  the  calculation  of  the 
amounts  of  carbon  monoxide,  hydrogen,  methane, 
and  nitrogen  existing  in  the  original  mixture.  The 
reactions  which  take  place  in  the  combustion  and 
the  volume  changes  due  to  these  reactions  are  the 
following  : l  — 

2  CO  +  O2  =  2  C02. 

2  vols.          1  vol.         2  vols. 

Contraction  in  burning  2  vols.  CO  =  1  vol. 
Hence  contraction  for  1  vol.  CO  =  J  vol. 

!Cf.  Vignon,  Bull.  Soc.  Chim.,  1897,  832. 


CHAP,  ii  ILLUMINATING  GAS  299 

2H2  +  0.,  =  2H20. 

2  vola.        1  vol.  liquid. 

Contraction  in  burning  2  vols.  H  =  3  vols. 
Hence  contraction  for  1  vol.  H  =  1.5  vols. 

CH4  +  2  O2  =  CO2  +  2  H2O. 

1vol.          2  vols.          1vol.  liquid. 

Contraction  in  burning  1  vol.  CH4  =  2  vols. 

From  the  above  equations  we  have  — 
Contraction  =  iCO  +  |H  +  2  CH4. 
Carbon  dioxide  formed  =  CO  +  CH4. 
Oxygen  consumed  =  £CO  +  iH  +  2  CH4. 


From  these  last  three  equations  a  variety  of  for- 
mulas for  the  calculation  of  the  various  components 
of  the  original  mixture  may  be  derived.  Noyes  and 
Shepard  give  — 

(1)  H  =  Contraction  minus  oxygen  consumed. 

(2)  CO  =  |(2  CO2  +  JH  minus  oxygen  consumed). 

(3)  CH4  =  CO2  -  CO. 

(4)  N  =  Original  volume  -  (H  +  CO  +  CH4). 

Instead  of  (2)  and  (3)  we  may  also  use  — 
CO  =  C02  -  CH4. 

2  Contraction  -  CO  -  3  H 


If  no  nitrogen  is  present  in  the  original  mixture 
the  following  equations  of  Vignon  may  be  employed, 


300 


GAS  ANALYSIS 


PART  III 


V  representing  the  volume  of  the  gas  mixture  taken 
for  the  combustion. 

H  =  V-  C02. 

CO  =  \  CO2  +  V-  I  contraction. 
CH4  =  |  CO2  +  |  contraction  -  V. 


I 

II 

III 

IV 

Volume  of  gas  residue 

ccm. 

ccm. 

ccm. 

ccm. 

taken     

83.45 

85.05 

83.05 

86.95 

Oxygen  added     .     .     . 

97.65 

96.25 

97.90 

99.95 

Total    .... 

181.10 

181.30 

180.95 

186.90 

Volume   after  combus- 

tion   .... 

.49.30 

46.95 

49.75 

49.50 

Contraction  resulting 

from  combustion    . 

131.80 

134.35 

131.20 

137.40 

Volume    after    absorp- 

tion of  carbon  dioxide 

13.05 

10.15 

13.75 

12.00 

Volume  of  carbon  di- 

oxide formed  in  the 

combustion    .     .     . 

36.25 

36.80 

36.00 

37.50 

Hydrogen  taken  for  de- 

termination of  excess 

of  oxygen    .... 

50.65 

40.80 

41.35 

40.90 

The     preceding  +  vol- 

ume remaining  after 

absorption  CO2     .     . 

63.70 

50.95 

55.10 

52.90 

Volume  after  combus- 

tion 

32.15 

28.30 

21.20 

24.75 

Contraction      resulting 

from  this  combustion 

31.55 

22.65 

33.90 

28.15 

Oxygen  in  excess  ($•  pre- 

ceding contraction)  . 

10.52 

7.55 

11.30 

9.38 

Oxygen  consumed  in 

combustion  of  CO, 

H,  and  CH4     .     .     . 

87.13 

88.70 

86.60 

90.57 

CHAP.    II 


ILLUMINATING   GAS 


301 


From  the  above  experimental  results  the  calculated 
percentages  of  the  various  gases  are  as  follows  :  — 


I 

II 

III 

IV 

Carbon  monoxide 

Per  cent 

6.2 

Per  cent 

6.1 

Per  cent 
6.2 

Per  cent 

6.0 

Hydrogen      . 
Methane  

53.5 
37.3 

53.7 
37.2 

53.7 
37.2 

53.9 
37.1 

Nitrogen  (difference) 

3.0 

3.0 

2.9 

3.0 

The  determination  of  oxygen  in  the  method  just 
described  takes  fully  as  much  time  as  the  direct 
absorption  of  carbon  monoxide,  and  it  is  therefore 
usually  advisable  to  first  separate  and  determine  the 
latter  gas  by  means  of  cuprous  chloride. 

In  carrying  on  the  various  combustions  by  which 
the  above  results  were  obtained,  it  was  observed 
that  a  much  stronger  current  is  required  to  maintain 
the  spiral  at  a  red  heat  in  an  atmosphere  of  gases  of 
low  molecular  weight  than  is  needed  with  heavier 
gases,  this  being  probably  due  to  the  different  ther- 
mal capacities  of  the  various  gases,  and  to  the  vary- 
ing velocities  of  the  different  gas  molecules.  This 
phenomenon  is  especially  marked  in  the  combus- 
tion of  hydrogen,  for  with  this  gas  it  is  necessary  to 
markedly  decrease  the  strength  of  the  current  as  the 
combustion  proceeds,  since  otherwise  a  current  which 
will  heat  the  spiral  only  to  redness  in  the  atmosphere 
of  hydrogen  at  the  beginning,  is  liable  to  melt  the 
platinum  wire  in  the  mixture  of  nitrogen  and  oxygen 
which  remains  after  the  combustion  is  completed. 

An  interesting  reaction  which  was  observed  during 


302  GAS  ANALYSIS  PART  in 

the  progress  of  the  work  is  that  a  mixture  of  methane 
and  water  vapour,  when  heated  by  the  spiral,  reacts 
as  follows  :  — 

CH4  +  H20  =  CO  +  3  IV 

According  to  this  equation  1  volume  of  methane 
should  yield  4  volumes  of  the  mixture  of  carbon 
monoxide  and  hydrogen.  On  actual  experiment  it 
was  found  that  24.1  ccm.  of  impure  methane  expanded 
to  74.5  ccm.,  from  which  cuprous  chloride  absorbed 
16.5  ccm.  This  16.5  ccm.  of  carbon  monoxide  shows 
that  an  equal  volume  of  methane  was  present  in  the 
original  gas,  and,  according  to  the  above  equation,  the 
16.5  ccm.  of  methane,  on  being  heated  in  the  pres- 
ence of  the  water  vapour,  should  show  an  increase 
in  volume  of  49.5  ccm.  The  expansion  observed  was 
50.4  ccm.,  a  result  which  is  sufficiently  close  to  sus- 
tain the  above  reaction.  That  the  observed  expan- 
sion does  not  agree  more  nearly  with  the  calculated 
increase  in  volume  is  doubtless  due  to  the  fact 
that  at  high  temperatures  carbon  monoxide  reacts 
with  water  vapour,  forming  carbon  dioxide  and 
hydrogen.2  That  this  actually  does  take  place  was 
ascertained  by  introducing  into  the  combustion 
pipette  79.75  ccm.  of  pure,  moist  carbon  monoxide, 
and  heating  the  spiral  for  five  minutes.  The  volume 
was  thereby  increased  to  82.75  ccm.  from  which 
3.05  ccm.  of  carbon  dioxide  were  absorbed  by  potas- 
sium hydroxide. 

1  Several  years  ago  Coquillion  observed  that  the  same  reaction 
takes  place  in  the  presence  of  a  red-hot  palladium  spiral.  —  Compt. 
rend.,  86,  1198. 

*Cf.  Dixon,  J.  Chem.  Soc.,  49,  99,  100. 


CHAP,  ii  ILLUMINATING  GAS  303 

5.    The  Determination  of  Sulphur 

The  sulphur  in  illuminating  gas  is  present  either 
as  hydrogen  sulphide,  or  as  carbon  disulphide,  or  as 
some  other  combination  with  carbon  and  hydrogen. 

Purified  illuminating  gas  should  be  free  from  hydro- 
gen sulphide.  The  hydrogen  sulphide  is  determined 
by  leading  the  'gas  through  a  suitable  absorption  ap- 
paratus containing  a  solution  of  lead  nitrate.  The 
resulting  lead  sulphide  is  filtered  off,  oxidised  in  a 
porcelain  crucible  with  nitric  acid,  treated  with  a  drop 
of  sulphuric  acid,  evaporated  to  dryness,  ignited,  and 
weighed. 

Bunte1  determines  the  hydrogen  sulphide  in  un- 
purified  gas  by  measuring  off  100  com.  of  the  gas  in 
one  of  the  gas  burettes  devised  by  him,  and  then 
allowing  a  solution  of  iodine  to  enter  until  it  is  no 
longer  decolourised  — 

H2S  +  I2  =  S  +  2  HI. 

The  iodine  solution  is  prepared  by  dissolving 
1.134  g.  of  pure  iodine  in  1  liter  of  water.  1  ccm. 
of  this  solution  corresponds  to  0.1  ccm.  of  hydrogen 
sulphide  at  0°  and  760  mm.  pressure.  The  sharp- 
ness of  the  reaction  can  be  increased  by  adding 
starch-paste,  the  iodine  being  then  added  until  the 
characteristic  blue  colour  of  the  iodide  of  starch  is 
seen. 

Hydrogen  sulphide  can  be  separated  from  carbon 
dioxide  by  means  of  manganese  dioxide,  this  substance 
holding  back  the  hydrogen  sulphide. 

Carbon  disulphide  can  be  separated  either  as  potas- 

1  Bunte,  Journal  fur  Gasbeleuchtung,  1888,  31,  898. 


304  GAS  ANALYSIS  PART  in 

slum  xanthogenate,  or  as  the  tri-ethyl  phosphorus 
compound. 

A.  Vogel  has  found1  that  the  smallest  amounts 
of  carbon  disulphide,  when  brought  into  a  solution 
of  potassium  hydroxide  in  alcohol,  form  potassium 
xanthogenate  — 


CS2  +  KOH  +  C2H5OH  =  OSC25  +  H2O. 


To  determine  carbon  disulphide,  the  gas  is  led 
through  an  alcoholic  solution  of  potassium  hydroxide, 
the  alcohol  is  evaporated,  acetic  acid  is  added  to  slight 
acid  reaction,  and  a  dilute  solution  of  cupric  acetate 
is  added.  If  carbon  disulphide  was  present,  a  yellow 
precipitate  results. 

A.  W.  Hofmann  has  given2  an  exceptionally  sharp 
reaction  for  carbon  disulphide.  If  a  gas  containing 
traces  of  carbon  disulphide  be  led  through  a  suitable 
absorption  apparatus  containing  a  solution  of  tri- 
ethyl-phosphine  in  ether,  the  liquid  turns  red,  and 
after  the  evaporation  of  the  ether  beautiful  ruby-red 
crystals  remain  — 

P(C2H6)8  +  CS2  =  P(C2H6)3CS2. 

Since,  however,  a  not  inconsiderable  portion  of 
the  sulphur  in  illuminating  gas  is  present  neither 
as  hydrogen  sulphide  nor  as  carbon  disulphide,  a 
determination  of  the  total  sulphur  of  the  gas  is 
usually  made. 

After  many  experiments,  the  author  is  of  the 
opinion  that  of  the  numerous  methods  which  have 

1  A.  Vogel,  Annalen  der  Chemie  und  Pharm.,  1853,  369. 

2  A.  W.  Hofmann,  Ibid.,  115,  293. 


CHAP,  ii  ILLUMINATING  GAS  305 

been  proposed  for  the  determination  of  the  total  sul- 
phur in  illuminating  gas,  the  following  is  the  best. 
This  is  essentially  the  method  of  Drehschmidt,  except 
that  in  the  place  of  a  Bunsen  burner  which  burns 
in  a  cylindrical  mantle  of  glass  there  is  used  a  small 
flame  burning  in  the  interior  of  a  large  glass  flask. 
•This  arrangement  is  preferable  to  that  of  Drehschmidt 
because  the  latter  in  the  hands  of  students  is  frequently 
broken. 

The  illuminating  gas  under  examination  is  measured 
in  an  experimental  gas-meter  and  then  passes  through 
a  short  piece  of  rubber  tubing  b  and  the  glass  tubing  c 
into  the  flask  A,  Fig.  92.  b  is  provided  with  a  screw 
pinchcock.  The  tube  c  is  of  hard  glass,  is  about  5 
mm.  in  diameter,  is  bent  somewhat  downward  after  it 
enters  the  flask  and  is  drawn  out  at  the  end  to  a  small 
opening.  The  neck  of  the  receiving  flask  A  is  drawn 
down  in  the  flame  of  the  blast  lamp  to  a  small  tube 
which  is  connected  at  d  by  means  of  a  piece  of  rub- 
ber tubing  with  the  absorption  apparatus  DD.  The 
three-way  glass  tube  e  is  inserted  in  the  tubulus  of 
the  flask  and  is  held  in  position  in  the  neck  by  a 
piece  of  rubber  tubing  or  a  rubber  stopper  with  a 
large  opening.  The  side  arm  of  the  three-way  piece 
e  is  joined  by  the  rubber  tube  /  to  the  cylinder  B. 
This  cylinder  is  filled  with  pieces  of  pumice-stone 
upon  which  there  is  allowed  to  drop  a  solution  of 
potassium  hydroxide  from  a  separatory  funnel.  The 
air  drawn  into  the  apparatus  must  pass  through  this 
tower  and  is  there  freed  from  any  hydrogen  sulphide 
which  may  be  present  in  the  air  of  the  laboratory. 
g  is  connected  with  an  ordinary  water  suction  pump. 

In  each  absorption  bottle  DD  is  placed  20  ccm.  of 


306 


GAS   ANALYSIS 


a  5  per  cent  solution  of  potassium  carbonate.     To  the 
contents  of  the  first  two  bottles  there  is  added  a  few 


FIG 


drops  of  bromine  to  oxidise  the  sulphur  dioxide  to 
sulphuric  acid. 

The  illuminating  gas  should  be  allowed  to  pass 
through  the  gas-meter  for  some  time  previous  to  the 
beginning  of  the  determination,  to  make  sure  that 


CHAP,  ii  ILLUMINATING   GAS  307 

the  meter  is  completely  filled  with  the  gas  under 
examination. 

When  the  apparatus  has  thus  been  prepared  for 
the  determination,  the  water  suction  pump  is  started, 
and  a  rapid  current  is  drawn  through  the  purifying 
cylinder  B,  the  flask  A,  and  the  bottles  DD.  The 
tube  c  is  withdrawn  from  the  flask,  and  the  gas 
is  ignited  at  its  outlet.  The  screw  pinchcock  b  is 
closed  until  the  flame  is  about  1  cm.  long,  and  c  is 
then  introduced  into  A  and  the  cork  h  is  firmly 
inserted  into  position,  c  should  be  moved  in  or  out 
through  h  until  the  flame  burns  in  the  middle  of  the 
flask.  It  should  lie  slightly  below  the  lower  side  of 
the  tubulus  of  the  flask.  In  this  position  the  flame 
will  burn  quietly  for  hours,  but  if  it  is  above  the 
tubulus  it  will  go  out,  because  in  the  upper  part  of 
the  flask  the  products  of  combustion  are  not  re- 
moved with  sufficient  rapidity  by  the  entering  cur- 
rent of  air.  By  means  of  the  screw  pinchcock  b  it  is 
easy  to  so  regulate  the  flame  as  to  cause  it  to  burn 
with  sharply  defined  edges,  thus  insuring  complete 
combustion  of  the  illuminating  gas. 

When  about  50  liters  of  the  gas  have  been  burned 
the  process  is  stopped,  the  flask  A  is  rinsed  out 
into  a  beaker,  and  the  contents  of  the  bottles  DD 
are  also  transferred  to  a  beaker.  The  liquid  is 
acidified  with  hydrochloric  acid,  is  then  boiled  to 
expel  the  bromine,  and  the  hot  solution  is  precipi- 
tated with  barium  chloride.  The  barium  sulphate  is 
separated  and  weighed  in  the  usual  manner,  and  the 
sulphur  found  is  calculated  for  100  ccm.  of  gas  at 
10°  C.  and  760  mm.  pressure.  If  50  liters  have  been 
used  for  the  determination,  and  if  t  denotes  the 


308  GAS  ANALYSIS  PART  in 

temperature  of  the  gas,  /  the  tension  of  aqueous 
vapour  at  this  temperature,  B  the  barometric  press- 
ure, and  p  the  weight  of  the  barium  sulphate,  then 
the  amount  of  sulphur  S  in  100  cubic  meters  of  the 
gas  is  — 

S  =  2000.  p.  0.13748  x  28 


Bromine  frequently  contains  sulphuric  acid  as  an 
impurity,  and  it  is  therefore  necessary  to  make  a 
second  solution  exactly  similar  to  that  which  has 
been  placed  in  the  bottles  DD,  and  to  determine  the 
sulphuric  acid  which  this  solution  contains,  subtract- 
ing then  the  amount  thus  found  from  that  resulting 
in  the  regular  analysis. 

6.    The  Determination  of  Ammonia 

Tieftrunk  determines  ammonia1  by  drawing  the 
gas  through  a  suitable  absorption  apparatus  contain- 
ing normal  acid,  and  measuring  the  volume  of  gas 
with  a  meter. 

If  unwashed  gas  is  being  examined  there  is  intro- 
duced between  the  meter  and  the  absorption  appa- 
ratus a  tube  filled  with  cotton,  and  a  wash-bottle 
containing  a  solution  of  sugar  of  lead  neutralised 
with  acetic  acid.  These  serve  to  hold  back  the 
hydrogen  sulphide  and  the  tar. 

By  titrating  back  the  normal  acid  the  amount  of 
ammonia  is  found. 

1  Cl.  Winkler,  Anleitung  zur  Untersuchung  der  Industrie-  Gase, 
Part  II,  p.  287. 


CHAP,  ii  ILLUMINATING  GAS  309 

If  the  gas  contains  very  much  tar,  the  normal  acid 
must  be  filtered  before  the  titration.  In  this  case  a 
measured  portion  of  the  solution  is  taken  for  the 
titration,  and  the  total  ammonia  is  calculated  there- 
from. 

7.    The  Determination  of  Carbon  Dioxide 

The  carbon  dioxide  can  be  determined  with  great 
exactness  with  the  apparatus  devised  by  Riidorff.1 
This  consists  of  a  three-necked  bottle  A  (Fig.  93) : 
in  one  neck  the  manometer  B,  filled  with  a  solution 
of  indigo,  is  inserted ;  in  the  second  neck  the  glass 
stopcock  pipette  (7,  graduated  in  tenths ;  and  in  the 
third  neck  either  a  single  glass  stopcock  or  a  double- 
bore  stopper  carrying  two  tubes,  one  of  which 
reaches  to  the  bottom  of  the  bottle,  while  the  other 
ends  just  below  the  stopper. 

The  exact  contents  of  the  bottle  must  be  known. 
In  making  the  determination,  illuminating  gas  is  led 
into  the  bottle  until  all  of  the  air  is  driven  out,  the 
lighter  gas  being  introduced  at  the  top  of  the  bottle 
and  the  heavier  air  passing  out  below.  The  stop- 
cocks are  now  closed,  and  the  manometer  is  brought 
to  zero  by  carefully  allowing  some  of  the  gas  which 
is  in  the  bottle,  and  which  is  under  pressure,  to 
escape.  If  now  a  solution  of  potassium  hydroxide 
be  allowed  to  drop  from  the  pipette  into  the  bottle, 
the  carbon  dioxide  will  be  absorbed.  The  volume 
of  the  carbon  dioxide  present  can  be  read  off  di- 
rectly from  the  pipette,  if,  after  the  absorption,  the 

1  Fogg.  Annal.,  125,  75;  also  Zeitschrift  fur  analyt,  Chemie, 
4,  231. 


310 


GAS  ANALYSIS 


PART  III 


manometer  is  again  brought  to  zero  by  admitting 
more  caustic  potash. 

In  this  determination  the  gas  must  of  course  be 
free  from  hydrogen  sulphide.    If  this  is  not  the  case, 


FIG. 


FIG.  94. 


the  gas  is  passed  through  manganese  dioxide  before 
entering  the  apparatus.      To  avoid  changes  of  tern- 


CHAP,  ii  ILLUMINATING  GAS  311 

perature  it  is  advisable  to  place  the  apparatus  in  a 
vessel  of  water  during  the  experiment. 

It  is  self-evident  that  the  apparatus  in  this  form 
is  influenced  by  changes  of  temperature  and  press- 
ure of  the  atmosphere.  It  can  be  made  independent 
of  these  by  attaching  a  Pettersson  compensating 
tube  to  the  manometer,  as  in  Fig.  94. 


CHAPTER   III 
ACETYLENE  GAS 

THE  growing  use  of  acetylene  gas  as  an  illuminant, 
the  ease  with  which  it  can  be  prepared  from  calcium 
carbide,  and  the  danger  which  may  result  from  the 
use  of  impure  gas,  or  badly  constructed  apparatus, 
or  improper  handling,  all  combine  to  make  the  cor- 
rect analysis  of  this  gas  or  of  mixtures  containing  it 
a  matter  of  considerable  importance. 

It  should  be  borne  in  mind  that  trustworthy  re- 
sults cannot  be  obtained  by  taking  a  small  piece  of 
calcium  carbide  from  the  lot  which  is  to  be  used  for 
the  preparation  of  acetylene,  bringing  this  sample 
into  a  small,  experimental  apparatus,  setting  free 
the  acetylene,  and  analysing  the  gas.  Commercial 
calcium  carbide  is  so  far  from  being  uniform  in  com- 
position that  it  is  absolutely  essential  to  prepare  an 
average  sample  from  a  large  amount  of  the  substance ; 
but  the  calcium  carbide  itself  is  very  hard  and  it  can- 
not be  pulverised  without  appreciable  loss,  owing  to 
the  ease  with  which  it  decomposes.  It  is  therefore 
best  to  analyse  the  gas  which  has  been  set  free  from 
a  considerable  portion  of  the  carbide. 

Commercial  calcium  carbide  is  frequently  con- 
taminated with  free  calcium,  calcium  phosphide, 
aluminium  carbide,  and  aluminium  sulphide.  Hence 

312 


CHAP,  in  ACETYLENE   GAS  313 

in  the  analysis  of  acetylene  the  following  gases  have 
to  be  considered  :  — 

1.  Acetylene.  5.  Methane. 

2.  Oxygen.  6.  Phosphine. 

3.  Nitrogen.  7.  Hydrogen  sulphide. 

4.  Hydrogen.  8.  Silicon  hydride. 

In  carrying  out  an  analysis  the  acetylene  is  first 
absorbed  by  fuming  sulphuric  acid  in  the  pipette 
shown  in  Fig.  82.  It  is  here  necessary  to  pass  the 
gas  repeatedly  into  the  pipette  until  no  diminution 
in  volume  is  noticed  upon  measuring  the  residual 
gas  in  the  burette.  Before  making  the  final  meas- 
urement, the  gas  must,  of  course,  be  passed  over  into 
the  caustic  potash  pipette  to  remove  the  fumes  of  the 
acid.  It  is,  however,  very  difficult  to  absorb  the  last 
traces  of  acetylene  by  this  method. 

Oxygen  is  now  absorbed  with  alkaline  pyrogallol. 
Phosphorus  cannot  be  used  for  this  purpose'  since 
even  small  quantities  of  acetylene  so  strongly  influ- 
ence the  absorption  of  oxygen  with  phosphorus  that 
it  is  impossible  to  obtain  even  approximately  correct 
results  for  oxygen  under  these  conditions. 

The  remainder  of  the  gas  is  now  passed  into  an 
ammoniacal  cuprous  chloride  solution  to  absorb  the 
last  trace  of  acetylene.  The  methane  and  hydrogen 
still  remaining  are  determined  by  combustion. 

If  only  an  oxygen  determination  is  to  be  made, 
a  small  quantity  of  alkaline  pyrogallol  is  drawn  into 
the  mercury  pipette  (Fig.  37),  and  this  reagent  is 
then  saturated  with  the  acetylene  gas  by  bringing 
into  the  pipette  about  100  ccm.  of  the  gas  and 


314  GAS   ANALYSIS  PART  m 

shaking.  The  oxygen  in  an  accurately  measured 
sample  is  then  determined  by  absorption  in  the 
usual  manner.  This  mode  of  procedure  is  neces- 
sary because  acetylene  belongs  to  those  gases  which 
are  quite  soluble  in  water. 

The  method  of  analysis  first  described  is,  however, 
to  be  preferred  because  the  chief  part  of  the  acetylene 
is  there  first  absorbed  with  fuming  sulphuric  acid, 
and  the  error  which  might  result  from  the  solubility 
of  acetylene  in  the  absorbent  is  then  minimised. 

It  is  always  possible  that  acetylene  gas  may  con- 
tain some  phosphine,  and  since  this  substance  is 
spontaneously  inflammable,  its  determination  is  of 
peculiar  interest  and  importance.  Lunge  has  pro- 
posed to  lead  the  gas  through  a  solution  of  sodium 
hypochlorite  and  then  gravimetrically  determine 
the  phosphoric  acid  which  is  formed.  Berge  and 
Reychler1  propose  passing  the  acetylene  through 
nitric  acid  which  contains  small  amounts  of  metallic 
salts,  or  of  leading  it  into  an  acid  solution  of  mer- 
curic chloride.  These  authors  found  in  1  cm.  of 
acetylene  (at  0°)  945  to  985  ccm.  of  phosphine  and 
1032  to  1417  ccm.  of  hydrogen  sulphide. 

A  very  good  method  for  the  determination  of 
phosphine,  hydrogen  sulphide,  and  silicon  hydride 
in  the  presence  of  one  another  consists  in  burning 
the  gas  mixture  in  the  apparatus  on  p.  306,  Fig.  92, 
and  then  gravimetrically  determining  the  resulting 
phosphoric  acid,  sulphuric  acid,  and  silica. 

There  is  no  doubt  that  these  methods  give  quite 
accurate  results ;  but  they  consume  so  much  time  as 
to  make  them  inferior  to  a  volumetric  method  which 

1  Bull.  Soc.  Chim.  [3],  17,  218. 


CHAP,  in  ACETYLENE   GAS  315 

4 

will  permit  of  the  separation  of  acetylene  from  phos- 
phine  and  will  enable  one  to  carry  out  an  analysis  in 
a  few  minutes.  For  this  reason,  the  author,  with  the 
aid  of  L.  Kahl,  experimented  with  a  number  of  solu- 
tions which  gave  promise  of  affording  a  method  of 
separation  of  phosphine  from  acetylene.  A  con- 
siderable volume  of  phosphine  was  first  prepared  by 
heating  an  alcoholic  solution  of  potassium  hydroxide, 
to  which  white  phosphorus  had  been  added.  The 
gas  was  collected  and  kept  over  water  in  a  glass 
gasometer.  It  contained  a  considerable  amount  of 
hydrogen  and  a  small  amount  of  air.  The  results 
given  below  cannot,  therefore,  lay  claim  to  complete 
scientific  accuracy.  The  acetylene  used  in  the  ex- 
periments was  prepared  fresh  each  time  in  an  appa- 
ratus similar  in  construction  to  the  Dobereiner  lamp. 

In  bringing  the  gases  into  contact  with  the  differ- 
ent reagents,  1  ccm.  of  the  reagent  was  first  drawn 
into  the  pipette  filled  with  mercury,  100  ccm.  of  the 
gas  was  then  introduced,  and  the  pipette  was  shaken 
for  three  minutes.  The  portion  of  the  gas  not 
then  absorbed  was  transferred  to  a  gas  burette  and 
measured.  If  the  reagent  acted  upon  mercury  it 
was  placed  in  a  small  bulb  absorption  apparatus, 
and  this  was  connected  with  a  mercury  gas  pipette 
on  the  one  side  and  with  a  gas  burette  on  the  other, 
and  the  absorption  was  brought  about  by  passing 
the  gas  mixture  backward  and  forward  through  the 
liquid  for  three  minutes. 

The  results  given  in  the  following  table  show  the 
number  of  cubic  centimeters  of  gas  which  1  ccm.  of 
the  reagent  in  question  was  able  to  absorb  under  the 
above  conditions. 


316 


GAS   ANALYSIS 


PART  III 


Reagent  employed 

Cubic 
entimeters 
of 
phosphine 
absorbed 

Cubic 
centimeters 
of 
acetylene 
absorbed 

I.  1  ccm.  of  hydrochloric  acid  cuprous 

chloride  made  by  Winkler's  method, 

p.  203      . 

39.8 

9.4 

II.  1  ccm.  of  hydrochloric  acid  cupric 

chloride  prepared  by  dissolving  10 

grams  of  crystallised  cupric  chloride 

CuCl2-2  H2O  in  100  ccm.  of  water 

and  adding  5  ccm.  of  concentrated 

hydrochloric  acid     .... 

8.6 

5.2 

III.  1  ccm.  of  a  sulphuric  acid  copper 

sulphate  solution  prepared  by  dis- 

solving 15.6  g.  crystallised   copper 

sulphate  CuSO4-5  H2O  in  100  ccm. 
of  water  and  adding  5  ccm.  of  dilute 

sulphuric  acid  (1  :  4  by  volume) 

8.8 

0.2 

IV.  1  ccm.    of    sodium   hypochlorite 

prepared    by    dissolving    10  g.    of 

crystallised    sodium    carbonate    in 

100  ccm.  of  water,  adding  an  excess 

of  bleaching  powder  and  filtering    . 

3.0 

0.6 

V.  1  ccm.  of  sodium  hypobromite  pre- 

Explosion occurred 

pared  by  dissolving  100  g.  of  caustic 
soda  in  1250  ccm.  of  water  and  add- 

when   this    reagent 
came  in  contact  with 

ing  25  g.  of  bromine 

the  gas  mixture. 

VI.  The  same  solution  as  under  V  but 

diluted  with  4  times  its  volume  of 

water       

.  .  . 

1.3 

VII.    Sodium   hypochlorite   prepared 

by  passing  chlorine  into  a  solution 

of  sodium  hydroxide.    This  solution 

was  brought  to  the  same  strength 

and  the  same  degree  of  alkalinity 

as  solution  V  by  the  addition  of  so- 

dium   hydroxide    and   water.      Its 

strength  was  determined  with  Pe- 

not's  solution  and  its  alkalinity  with 

normal  sulphuric  acid 

0.7 

CHAP.  Ill 


ACETYLENE  GAS 


317 


Cubic 

Cubic 

centimeters 

centimeters 

Reagent  employed 

of 

of 

phosphine 

acetylene 

absorbed 

absorbed 

VIII.    Potassium  permanganate,  5  per 
cent  solution    

3.2 

2.6 

1.25  per  cent  solution 

1.0 

1.2 

IX.  Silver  nitrate,  3  per  cent  solution 

.  .  . 

1.6 

X.  Nitric    acid    solution    of    copp'er 

sulphate  prepared  by  dissolving  78  g. 
of  copper  sulphate  CuSO4  •  5  H2O  in 

a  mixture  of  250  ccm.  of  concen- 

trated nitric  acid  and  250  ccm.  of 

water       

1.2 

0.8 

The  above  results  show  that  of  the  solutions  which 
were  examined  the  sulphuric  acid  solution  of  copper 
sulphate  is  the  best  absorbent  for  the  separation  of 
phosphine  and  acetylene. 

Many  attempts  were  then  made  to  carry  out  this 
method  of  absorption  in  gas  pipettes,  but  it  was  soon 
found  that  the  action  of  light  had  great  influence 
upon  the  results.  In  attempting  to  saturate  a  sul- 
phuric acid  solution  of  copper  sulphate  with  acetylene 
gas,  the  reagent  being  contained  in  a  double  gas 
pipette,  it  was  found  that  even  in  diffused  daylight 
the  copper  solution  took  up  further  amounts  of  acety- 
lene upon  standing.  The  same  result  was  obtained 
with  sodium  hypochlorite.  Careful  study  of  this  re- 
action showed  further  that  the  behaviour  of  acetylene 
gas  when  brought  into  contact  with  copper  sulphate 
alone  is  very  different  from  its  behaviour  when  brought 
into  contact  with  copper  sulphate  and  metallic  mer- 
cury in  the  presence  of  phosphine.  We  have  found 


318  GAS   ANALYSIS 


PART  III 


that  when  mercury  and  an  excess  of  copper  sulphate 
are  present  the  diminution  in  volume  which  should 
result  from  the  absorption  of  the  phosphine  in  the 
acetylene  gas  corresponds  exactly  to  four  times  the 
volume  of  the  phosphine  present. 

Experiments  were  next  made  to  ascertain  whether 
acetylene  which  is  free  from  phosphine  behaves  dif- 
ferently when  brought  into  contact  with  copper  sul- 
phate alone  or  with  copper  sulphate  and  mercury. 
Acetylene  which  had  been  completely  freed  from  all 
phosphine  by  treatment  with  copper  sulphate  was 
passed  into  a  small  bulb  apparatus  containing  copper 
sulphate  and  into  another  apparatus  containing  copper 
sulphate  and  mercury.  The  measurement*  showed 
that  2  ccm.  of  an  acid  copper  sulphate  solution  ab- 
sorbed exactly  the  same  amount,  0.4  ccm.,  of  acety- 
lene in  each  case. 

The  experiments  with  mixtures  of  acetylene  and 
phosphine  were  complicated  by  the  fact  that  phos- 
phine when  exposed  to  the  light  and  in  contact  with 
water  containing  air  decomposes  with  the  separa- 
tion of  phosphorus  and  the  formation  of  water,  a 
behaviour  which  renders  it  extremely  difficult  to  pre- 
pare mixtures  of  the  two  gases  of  accurately  known 
composition.  . 

The  results  given  below  were  obtained  by  mixing 
carefully  measured  amounts  of  acetylene  and  phos- 
phine in  a  gas  burette  filled  with  mercury.  The  phos- 
phine was  prepared  in  the  manner  above  described. 

Direct  absorption  with  bromine  water  in  an  ab- 
sorption pipette  showed  a  diminution  in  volume  of 
25.8  ccm.  when  the  reagent  acted  upon  a  mixture 
of  50.4  ccm.  of  nitrogen  and  48.2  ccm.  of  phosphine. 


CHAP,  in  ACETYLENE    GAS  319 

A  second  treatment  of  this  gas  residue  with  the  same 
absorbent  gave  no  further  diminution  in  volume. 
The  purity  of  the  phosphine  was  thus  ascertained  to 
be  53.5  per  cent. 

A  mixture  of  94  ccm.  of  nitrogen  and  2  ccm.  of 
this  phosphine  gave  upon  absorption  with  copper  sul- 
phate solution  a  diminution  of  1  ccm.  corresponding 
to  50  per  cent  of  phosphine  in  that  gas. 

A  mixture  of  91.8  ccm.  of  nitrogen  and  2.2  ccm.  of 
phosphine  gas  and  copper  sulphate  gave  a  diminution 
of  1.1  ccm.  corresponding  to  50  per  cent. 

A  mixture  of  94  ccm.  of  nitrogen  and  5.2  ccm.  of 
phosphine  gave  3  ccm.  corresponding  to  57.6  per  cent. 

A  mixture  of  91.6  ccm.  of  nitrogen  and  5.2  ccm. 
of  phosphine  gave  3  ccm.  corresponding  to  57.1  per 
cent. 

A  mixture  of  94.3  ccm.  of  nitrogen  and  2.9  ccm. 
of  phosphine  gave  1.5  ccm.  corresponding  to  51.7  per 
cent. 

All  experiments  were  carried  out  with  the  greatest 
care.  The  variation  in  the  results  is  to  be  explained 
by  the  decomposition  of  the  phosphine  by  the  oxygen 
dissolved  in  the  water  and  by  the  action  of  light. 
Since  it  is  necessary  to  keep  the  containing  vessels 
moist  in  order  to  exclude  errors  resulting  from  the 
tension  of  aqueous  vapour,  it  is  impossible  to  avoid 
the  above  error  even  when  working  with  apparatus 
filled  with  mercury.  The  following  values  show, 
nevertheless,  that  an  acid  copper  sulphate  solution  in 
an  apparatus  filled  with  mercury  is  a  very  good  absorb- 
ent for  the  removal  of  phosphine  from  acetylene  gas. 

The  mean  value  obtained  for  the  purity  of  the 
phosphorus  employed  was  52.4  per  cent. 


320 


GAS   ANALYSIS 


Mixtures  of  acetylene  and  phospbine  when  shaken 
with  mercury  and  3  ccm.  of  an  acid  copper  sulphate 
solution  which  had  previously  been  saturated  with 
acetylene  gave  the  results  tabulated  below.  The 
copper  sulphate  solution  was  prepared  as  described 
under  Experiment  III  on  p.  316. 

Another  cause  for  a  lack  of  uniformity  in  the 
results  is  to  be  found  in  the  difficulty  of  keeping 
the  reagent  saturated  always  to  the  same  degree 
with  acetylene  gas. 

To  determine  the  phosphine  in  a  sample  of  acety- 
lene gas,  measure  off  the  gas  in  a  gas  burette  filled 
with  mercury,  and  then  pass  the  sample  over  into 
a  gas  pipette  filled  with  mercury  and  containing 
3  ccm.  of  an  acid  copper  sulphate  solution  which  has 
been  prepared  as  above  described  and  which  has 
been  previously  saturated  with  acetylene  by  shaking 
it  with  a  sufficient  amount  of  this  gas.  Shake  the 
gas  mixture  with  the  reagent  for  three  minutes  and 
then  measure  the  remaining  volume.  The  fourth 
part  of  the  diminution  in  volume  thus  found  repre- 
sents the  volume  of  phosphine  present. 


Volume  of 
Acetylene 
Gas  Used 

Volume 
of  52.4 
per  cent 
Phosphine 

Volume  of 
Phosphine 
Present 

Observed 
Diminu- 
tion in 
Volume 

Volume  of  Phosphine 
found  in  the  Experiment, 
assuming  that  it  corre- 
sponds to  one-fourth  of 
the  observed  diminution 

Used 

in  Volume 

92.8 

5.6 

2.90 

11.2 

2.80 

90.2 

7.4 

3.90 

13.4 

3.40 

94.6 

2.4 

1.20 

4.6 

1.15 

92.2 

5.2 

2.70 

10.6 

2.65 

94.0 

3.2 

1.67 

8.3 

2.0 

82. 

5.4 

2.82 

11.0 

2.75 

CHAP,  in  ACETYLENE   GAS  321 

A  large  number  of  analysts  have  found  that 
acetylene  gas  contains  sulphur;  but  since  the  gas 
is  evolved  from  a  strongly  alkaline  liquid,  it  is 
probable  that  the  sulphur  which  is  present  is  chiefly 
in  the  form  of  organic  sulphur  compounds  and  is  not 
present  as  hydrogen  sulphide. 


CHAPTER  IV 

GASES  WHICH  OCCUR  IN  THE  MANUFACTURE 
OF  SULPHURIC  ACID 

IN  the  manufacture  of  sulphuric  acid  the  gases 
which  engage  the  attention  of  the  analyst  are :  — 

1.  Sulphur  dioxide;  it  may  also  be  desired  here 
to  determine  at  the  same  time  the  small  amount  of 
sulphur  trioxide  present. 

2.  Nitrous  oxide. 

3.  Nitric  oxide. 

4.  Nitrogen  trioxide. 

5.  Nitrogen  peroxide. 

6.  Oxygen. 

The  examination  of  the  gas  mixture  for  nitrous 
oxide  and  nitrogen  peroxide  is  very  rarely  desired. 

1.    Sulphur  Dioxide 

In  the  manufacture  of  sulphuric  acid  the  deter- 
mination of  the  sulphur  dioxide  in  the  kiln-gases 
is  of  especial  importance.  Reich's  method1  has 
been  universally  adopted  for  this  purpose.  Reich's 
apparatus  consists  of  a  double-necked  absorption 
bottle  A,  the  aspirator  B,  and  the  glass  cylinder  E. 

1  F.  Reich,  Berg-  und  Huttenmann,  Zeitung,  1858 ;  also  Cl. 
Winkler,  Anleitung  zur  Untersuchung  der  Industrie-Gase,  Part  II, 
pp.  118  and  353. 


CHAP,  iv     GASES   OF   SULPHURIC   ACID  PROCESS 


323 


These  are  supported  by  a  wooden  stand,  as  shown 
in  Fig.  95.  The  rubber  tube  joining  A  and  B  is 
about  30  cm.  long.  A  is  half  filled  with  water,  and 
10  or  20  ccm.  of  a  -^  normal  iodine  solution  are 
added.  The  aspirator  B  is  filled  with  water. 

Before  making  a  determination,  the  air  in  the 
tubes  leading  to  the 
apparatus  is  displaced 
by  the  gas  to  be  ex- 
amined. The  appara- 
tus is  tight  if,  after 
a  short  time  and  as 
soon  as  the  air  in 
A  is  correspondingly 
expanded,  the  water 
ceases  entirely  to  flow 
from  the  aspirator. 

In  making  a  deter- 
mination the  stopcock 
0  is  opened,  and  the 
amount  of  water  which 
is  necessary  to  draw 
over  sufficient  gas  to 
decolour  the  iodine 
solution  is  measured 
in  the  cylinder  E. 

During  the  experiment  the  bottle  A  is  shaken.  The 
volume  of  the  water  which  has  run  out  is  equal  to 
that  of  the  gas  taken,  less  the  volume  of  the  sulphur 
dioxide  absorbed  in  J.,  and  the  quantity  of  sulphur 
dioxide  present  can  be  told  from  the  amount  of  iodine 
used.  Hence  the  per  cent  of  sulphur  dioxide  present 
can  be  easily  calculated.  In  accurate  work  the  vari- 


95. 


324  GAS  ANALYSIS  PART  in 

ations  of  temperature  and  pressure  must  of  course  be 
taken  into  account. 

When  10  com.  of  -^  normal  iodine  solution  are 
used  all  calculation  may  be  avoided  by  using  the 
following  table,  given  by  Lunge  in  his  book  on  the 
Soda  Manufacture :  — 

Water  from  Aspirator,  Volume  per  cent  of 

ccm.  SO2  in  the  Gas 

82  12.0 

86  11.5 

90  11.0 

95  10.5 

100  10.0 

106  9.5 

113  9.0 

120  8.5 

128  8.0 

138  7.5 

148  7.0 

160  6.5 

175  6.0 

192.  5.5 

212  5.0 

Provided  that  6  per  cent  by  volume  of  oxygen 
is  present  in  the  kiln-gases  when  they  leave  the 
lead-chamber,  the  gases  should  contain,  according 
to  Gerstenhofer,1  10.65  per  cent  of  sulphur  dioxide 
when  sulphur  is  burned,  and  8.8  per  cent  when 
pyrites  is  roasted. 

If  considerable  amounts  of  nitric  oxide,  nitrogen 
trioxide,  nitrogen  peroxide,  or  nitric  acid  are  mixed 
with  the  gases  containing  the  sulphur  dioxide,  the 

1  Robert  Hasenclever  in  A.  W.  Hofmann's  Bericht  uber  d.  Ent- 
wickelung  d.  chem.  Industrie,  Part  I,  p.  170. 


CHAP,  iv     GASES   OF  SULPHURIC   ACID  PROCESS 


325 


iodine   method   cannot   be   used,   and   it  is  best  to 
determine  the  sulphur  dioxide  gravimetrically. 

To  determine  sulphur  trioxide  in  the  presence 
of  sulphur  dioxide,  the  mixture  of  the  two  gases 
is  led  through  a  standardised  solution  of  iodine ; l 
the  amount  of  the  iodine  acted  upon  by  the  sul- 
phur dioxide  is  determined  with  sodium  arsenite, 
and  after  acidifying  with  hydrochloric  acid,  the  sul- 
phuric acid  is  precipitated  by 
barium  chloride.  Lunge  and 
Salathe  have  shown  that  it  is 
difficult  to  hold  back  sulphur 
trioxide  with  ordinary  absorp- 
tion apparatus.  They  have  used 
with  success  the  arrangement 
shown  in  Fig.  96.  A  is  an 
ordinary  bottle.  The  exit  tube 
b  is  filled  with  glass  beads,  and 
at  the  lower  end  it  is  blown  out 
to  a  bulb  which  is  pierced  with 
holes.  The  gas  to  be  examined 
enters  through  # ,  passes  through 
the  liquid  and  then  through  the 
tube  b.  By  sliding  the  tube  b 
up  and  down,  a  position  may 
easily  be  found  in  which  the  gas  will  carry  along 
with  it  small  amounts  of  the  absorbing  liquid,  and 
will  thus  keep  the  glass  beads  constantly  moistened 
with  the  reagent. 

Lunge  and  Salathe  used  three  such  wash-bottles  in 
determining  the  sulphur  trioxide  in  kiln-gases. 

1  G.  Lunge  and  F.  Salathe,  Berichte  der  deutschen  chemischen 
Gesellschaft,  1877,  1824, 


FIG.  96. 


326  GAS   ANALYSIS  PART  in 

2.    Nitrous  Oxide 

Up  to  the  present  time  nitrous  oxide  has  not  been 
detected  with  certainty  in  the  gases  of  a  sulphuric 
acid  manufactory.  It  is,  however,  quite  probable 
that  this  gas  may  be  formed.  Very  small  amounts 
cannot  be  determined,  but  when  the  quantity  rises  to 
about  0.3  per  cent  it  can  be  determined  by  burning  it 
with  hydrogen  in  the  explosion  pipette,  after  all  the 
absorbable  gases  have  been  removed.  It  must  not  be 
forgotten  that  nitrous  oxide  is  very  soluble  in  water, 
and  that  for  this  reason  the  absorbents  must  be  care- 
fully saturated  with  those  gases  which  they  do  not 
absorb. 

3.    Nitric   Oxide 

Nitric  oxide  may  occur  in  irregular  working  of  the 
lead-chamber. 

For  determining  the  nitric  oxide  in  chamber-gases, 
Cl.  Winkler  has  proposed l  that  the  gases  be  led  first 
through  a  concentrated  solution  of  potassium  hy- 
droxide, and  then,  with  addition  of  air,  through  two 
small  absorption  cylinders  containing  concentrated 
sulphuric  acid.  The  amount  of  the  nitrogen  trioxide 
thus  formed  is  determined  by  titration  with  potassium 
permanganate,  or  by  decomposition  in  the  nitrometer. 
At  least  from  3  to  5  liters  should  be  taken. 

4.    Nitrogen  Trioxide 

Cl.  Winkler  has  determined2  the  nitrogen  trioxide 
in  chamber  gases  by  leading  them  through  2  to  5  ccm. 

1  Cl.  Winkler,  Anleitung  zur  Untersuchung  der  Industrie^Grase, 
Part  II,  p.  314.  2  Ibidt }  p.  304. 


CHAP,  iv     GASES   OF   SULPHURIC   ACID   PROCESS  327 

of  y^Q  potassium  permanganate,  which  had  been  previ- 
ously acidified  with  sulphuric  acid,  and  had  also  been 
somewhat  diluted,  until  the  permanganate  solution 
was  decoloured.  The  per  cent  can  then  be  calculated 
from  the  amount  of  water  which  has  flowed  from  the 
aspirator,  as  is  done  in  Reich's  method. 

Agreeing  results  were  obtained  by  the  above 
method  when  the  nitric  acid  was  first  absorbed  by 
concentrated  sulphuric  acid,  and  was  then  titrated 
with  ~Q  potassium  permanganate. 

5.    Nitrogen  Peroxide 

In  the  manufacture  of  sulphuric  acid  the  nitrogen 
peroxide  which  comes  in  question  is  always  accom- 
panied by  nitrogen  trioxide.  'According  to  Winkler 
and  Lunge  the  nitrogen  peroxide  can  be  best  deter- 
mined by  first  absorbing  the  nitrogen  peroxide  and 
nitrogen  trioxide  together  by  concentrated  sulphuric 
acid.  A  portion  of  the  solution  thus  obtained  is 
titrated  with  -^  potassium  permanganate,  and  in  the 
other  portion  the  gases  are  determined  as  nitric  oxide 
in  the  nitrometer. 

6.    Oxygen 

To  determine  the  per  cent  of  oxygen  in  the  chamber- 
gases,  all  of  the  acid  constituents  are  first  removed 
by  absorption  with  potassium  hydroxide,  and  the  oxy- 
gen is  then  absorbed  with  phosphorus  as  suggested 
by  Lindemann. 


CHAPTER  V 

ANALYSIS    OF   THE    GASES   EVOLVED    IN   THE 
ELECTROLYSIS   OF   CHLORIDES 

IN  the  development  of  electrolytic  processes  for  the 
preparation  of  chlorine  and  caustic  alkalies  the  analy- 
sis of  the  gases  which  are  evolved  furnishes  a  method 
of  control  over  the  process  and  is  therefore  of  first 
importance.  The  gases  coming  from  the  anode  will 
contain,  in  addition  to  free  chlorine,  both  oxygen  and 
carbon  dioxide,  and  in  the  mercury  processes  hydro- 
gen may  also  appear.  The  current  yield  is  the  better 
the  higher  the  percentage  of  chlorine  in  the  gases 
and  the  lower  the  amount  of  oxygen  and  carbon 
dioxide. 

Analytical  results  of  sufficient  accuracy  for  practi- 
cal purposes  are  obtained  by  drawing  the  gases  into 
a  simple  gas  burette  filled  with  water,  reading  at 
once  the  gas  volume  thus  drawn  off,  and  then,  with 
the  aid  of  a  small  5  ccm.  pipette,  introducing  into  the 
burette  through  the  rubber  tube  at  its  top  a  50  per 
cent  solution  of  potassium  iodide.  Upon  shaking  the 
gas  with  this  reagent  all  chlorine  is  at  once  absorbed 
while  carbon  dioxide,  oxygen,  hydrogen,  and  nitrogen 
remain  behind.  The  gas  is  then  passed  into  a  potas- 
sium hydroxide  pipette  to  absorb  the  carbon  dioxide 
and  is  transferred  to  a  pipette  for  solid  and  liquid 
reagents  (see  p.  52)  containing  metallic  copper, 

328 


CHAP,  v    GASES  FROM  CHLORIDE   ELECTROLYSIS         329 

ammonia,  and  ammonium  carbonate  solution.  These 
will  absorb  the  oxygen.  Hydrogen  is  determined 
by  combustion,  using  one  of  the  methods  described 
in  Part  II,  Chapter  III,  pp.  130  to  143. 

Gases  which  are  evolved  under  other  conditions, 
especially  in  electrolytic  processes  that  are  carried  on 
without  diaphragms,  consist  chiefly  of  hydrogen  and 
oxygen.  The  oxygen  in  such  a  mixture  may  best  be 
absorbed  with  the  copper  pipette  mentioned  above. 
The  use  of  phosphorus  is  dangerous  because  of  the 
occasional  occurrence  of  an  explosion. 


CHAPTER   VI 


DETERMINATION  OF  THE  GASES  WHICH  OCCUR  IN 
THE  MANUFACTURE  OF  BLEACHING  POWDER 

1.    Determination  of  the  Amount  of  Chlorine  in 
the  Chamber -air 

THE  determination  of  chlorine  in  chamber-air  is 
accomplished  by  the  use  of  a  solution  of  potassium 
iodide  and  sodium  arsenite,  with  the 
addition  of  calcium  carbonate.1  The 
apparatus  which  is  employed  is  shown 
in  Fig.  97.  It  consists  of  a  glass 
cylinder  E  provided  with  a  two-hole 
rubber  stopper,  through  one  opening 
of  which  is  inserted  the  glass  tube  D 
passing  nearly  to  the  bottom  of  the 
cylinder.  The  outer  end  of  D  must 
be  drawn  out  to  an  opening  no  larger 
than  a  small  needle.  Through  the 
other  opening  of  the  stopper  there  is 
inserted  a  short  tube  B,  which  has  a 
small  opening  in  the  side,  and  to  the 
upper  end  of  this  tube  is  attached  a 
rubber  bulb  of  about  100  ccm.  capacity. 
There  is  first  placed  in  E  26  ccm.  of  the 
iodide-arsenite  solution,  to  which  has  been  added  a 
little  starch  paste.  The  solution  is  prepared  by  dis- 

1  Lunge,  Sulphuric  Acid  and  Alkali,  2d  ed.,  3,  458. 
330 


FIG.  97. 


CHAP,  vi     GASES  IN  BLEACHING  POWDER  PROCESS    331 

solving  0.3485  g.  of  arsenious  acid  in  sodium  car- 
bonate, and  neutralising  this  with  sulphuric  acid,  then 
adding  25  g.  of  potassium  iodide,  5  g.  of  precipitated 
calcium  carbonate,  and  6  to  10  drops  of  ammonia, 
the  whole  being  finally  diluted  to  1  liter  with  water. 
The  outer  end  of  D  is  inserted  into  an  opening  in  the 
side  of  the  chamber,  about  two  feet  from  the  bottom. 
The  bulb  A  is  then  tightly  compressed  with  the 
hand,  the  hole  in  the  side  of  B  is  closed  with  the 
finger,  and  the  pressure  on  A  is  released.  The  ex- 
pansion of  the  bulb  draws  the  chamber-air  from  D 
and  through  the  liquid  in  E.  The  operation  is  con- 
tinued until  the  liquid  in  the  cylinder  shows  a  colour, 
the  number  of  compressions  of  A  being  noted.  If 
the  capacity  of  the  bulb  is  about  100  ccm.  C^io^ 
cubic  foot),  then  the  appearance  of  colour  with  10 
aspirations  indicates  2^  gr.  of  chlorine  per  cubic  foot, 
or  5  gr.  with  5  aspirations. 

The  chlorine  can  also  be  determined  by  drawing 
it  through  absorption  bottles  containing  an  aqueous 
solution  of  potassium  iodide,  and  titrating  the  liber- 
ated iodine  with  ^  arsenious  acid. 

2.    Determination  of  Chlorine  in  the  Presence  of 
Hydrochloric  Acid  G-as1 

These  gases  occur  together  in  the  mixture  coming 
from  the  decomposers  of  the  Deacon  process.  5 
liters  of  the  gas  mixture  is  drawn  through  3  gas 
wash-bottles,  which  together  contain  250  ccm.  of  a 
solution  of  sodium  hydroxide,  whose  specific  gravity 
is  1.076.  After  the  gas  has  been  passed  through 

1  Neumann,  Gas  Analyse  und  Gasvolumetrie,  1901,  p.  146. 


332  GAS  ANALYSIS  PART  in 

these  bottles,  the  liquid  in  the  three  is  united  and 
diluted  to  500  ccm.  100  ccm.  of  this  solution  is 
then  placed  in  a  flask  fitted  with  a  Bunsen  valve, 
and  an  excess  of  a  solution  of  ferrous  sulphate1  is 
added.  The  latter  is  then  boiled,  diluted  with 
200  ccm.  of  water,  and  titrated  back  with  |  potas- 
sium permanganate.  This  gives  the  amount  of  free 
chlorine. 

To  another  portion  of  10  ccm.  of  the  solution 
some  sulphur  dioxide  is  added,  and  the  liquid  is 
then  acidified  with  sulphuric  acid,  boiled,  cooled, 
and  the  free  sulphur  dioxide  destroyed  by  the  addi- 
tion of  potassium  permanganate.  The  solution  is 
now  neutralised  with  sodium  carbonate,  diluted,  and, 
after  addition  of  potassium  dichromate,  is  titrated 
with  ~Q  silver  nitrate  solution.  This  gives  the  total 
chlorine  (C1  +  HC1). 

1 100  g.  FeS04  and  100  g.  concentrated  H2S04  in  1  liter. 


CHAPTER  VII 
THE  ANALYSIS  OF  ATMOSPHERIC  AIR 

IN  the  analysis  of  atmospheric  air,  the  chemist  has 
to  deal  with  the  following  constituents :  — 

1.  Aqueous  vapour. 

2.  Carbon  dioxide. 

3.  Carbon  monoxide. 

4.  Oxygen. 

5.  Ozone. 

6.  Argon. 

7.  Sulphur  dioxide  and  sulphuric  acid. 

8.  Nitrogen. 

For  sanitary  purposes,  the  determinations  of  car- 
bon dioxide  and  water  are  those  most  frequently 
desired. 

1.    The  Determination  of  Aqueous  Vapour  in  the 
Atmosphere 

The  water  can  be  determined  with  great  exact- 
ness by  leading  a  measured  or  weighed  volume  of 
air  through  tubes  filled  with  calcium  chloride  or 
phosphorus  pentoxide,  and  ascertaining  their  in- 
crease in  weight.  It  hardly  need  be  mentioned  that 
the  calcium  chloride  must  first  be  treated  with  car- 
bon dioxide,  so  that  it  may  contain  no  basic  salt 

333 


334  GAS  ANALYSIS  PART  m 

which,  by  taking  up  carbon  dioxide,  could  change 
in  weight.  The  common  phosphorus  pentoxide  is 
never  pure,  but  always  contains  traces  of  phosphorus 
and  phosphorous  acid.  For  this  reason,  a  current  of 
dry  air  should  be  led  for  some  time  through  the  ab- 
sorption apparatus  before  it  is  used. 

Pettersson  has  devised  an  admirable  apparatus 
with  which  the  moisture  and  carbon  dioxide  of  the 
atmosphere  can  be  directly  determined  volumetri- 
cally.  (See  the  determination  of  carbon  dioxide  in 
air,  p.  346.) 

For  most  purposes  the  hair  hygrometer  and  the 
psychrometer  give  sufficiently  accurate  results. 

A  very  fine  form  of  the  hair  hygrometer  devised 
by  Saussure  is  made  by  Hermann  Pfister,  in  Berne. 

The  construction  of  the  instrument  is  based  upon 
the  property  possessed  by  hair  from  which  the  oil 
has  been  removed,  of  lengthening  or  shortening  ac- 
cording to  the  amount  of  moisture  in  the  air.  By 
alternately  moistening  and  drying  the  hair  thor- 
oughly for  a  number  of  times,  it  is  given,  according 
to  Pfister,  the  property  of  quite  regular  expansion. 

Figure  98  shows  the  arrangement.  A  hair,  prepared 
as  above  mentioned,  is  fastened  to  a  suitable  frame. 
The  hair  passes  around  a  little  wheel  below,  and  the 
changes  in  length  cause  the  pointer  to  move  and 
ifive  the  relative  moisture  directly  on  the  scale. 

August's  psychrometer  is  based  on  the  fact  that 

iter  exposed  to  the  air  evaporates  the  more  rapidly, 
aid  thereby  extracts  more  heat  from  its  surround- 
ings, the  farther  the  air  is  removed  from  the  condition 
of  saturation.  From  the  lowering  of  the  tempera- 
ture (t  —  t1)  of  a  thermometer  which  has  been  moist- 


CHAP,  vii      ANALYSIS   OF  ATMOSPHERIC  AIR  335 


FIG.  98. 


336  GAS   ANALYSIS  PART  in 

ened  in  a  suitable  manner,  the  tension  e  of  the  water 
vapour  in  the  air  is  calculated  from  the  formula  — 


in  which  el  is  the  tension  corresponding  to  the  tem- 
perature t\  b  the  barometric  pressure  in  millimeters, 
and  k  an  empirical  factor  which  has,  according  to 
the  researches  of  Regnault,  the  following  values  :  — 

In  small  closed  rooms       ....  0.00128 

"  large  "  ....  0.00100 

"  halls  with  open  windows     .        .        .  0.00077 

"  courts  ......  0.00074 

"  open  air  (no  wind)      ....  0.00090 

2.    The  Determination  of  Carbon  Dioxide  in  the 
Atmosphere 

The  most  varied  experience  has  shown  that 
through  the  process  of  breathing  the  air  acquires 
properties  which  cause  it  to  act  deleteriously  upon 
health  when  the  products  of  breathing  exceed  a 
certain  limit.  Since  we  are  not  able  by  ordinary 
means  to  determine  the  other  substances  which  are 
here  formed,  we  make  use  of  Pettenkofer's  sugges- 
tion and  judge  of  the  purity  of  the  air  by  the  per 
cent  of  carbon  dioxide  present. 

According  to  Pettenkofer,  the  carbon  dioxide  in 
the  air  should  not  be  raised,  by  breathing,  to  over 
0.1  per  cent. 

The  process  best  suited  to  the  quantitative  deter- 
mination is  that  first  used  by  Saussure  and  modified 
by  Pettenkofer  :  it  consists  in  absorbing  the  carbon 


CHAP,  vii      ANALYSIS  OF  ATMOSPHERIC   AIR  337 

dioxide  of  a  measured  volume  of  air  with  a  barium 
hydroxide  solution  of  known  strength,  and  then  de- 
termining, by  titration  with  oxalic  acid,  the  amount 
of  barium  hydroxide  still  unacted  upon.  This 
method  has  been  used  by  many  investigators,  and 
has  been  modified  in  minor  details.  A  very  practi- 
cal form  is  that  devised  by  W.  Hesse. 

Clemens  Winkler1  describes  the  method  as  fol- 
lows :  — 

"  W.  HESSE'S  METHOD.2 — This  method  is  superior 
to  the  method  of  Pettenkofer,  upon  which  it  is 
based,  in  that  it  simplifies  and  shortens  the  deter- 
mination of  carbon  dioxide,  and  can  also  be  carried 
out  at  the  place  where  the  sample  is  taken,  the  pos- 
sibility of  employing  it  being  thus  much  greater 
than  formerly.  By  lessening  the  volume  of  the  air 
to  be  examined,  it  became  possible  to  diminish  the 
size  of  the  apparatus  to  portable  form  without  lim- 
iting thereby  the  number  of  determinations. 

"  The  necessary  apparatus  may  be  divided  into  a 
stationary  and  a  portable  portion. 

"  A.  The  reserve  apparatus  in  the  laboratory  com- 
prises the  following :  — 

"  1.  A  glass  balloon  or  large  bottle  holding  sev- 
eral liters,  and  filled  with  a  concentrated  solution  of 
barium  hydroxide.  1  kg.  of  barium  hydroxide  and 
50  g.  of  barium  chloride  are  put  into  from  4  to  5  kg. 
of  distilled  water.-  As  the  solution  is  used  it  is  re- 

1  Cl.  Winkler,  Anleitung  zur  Untersuchung  der  Industrie-Gase, 
Part  II,  p.  375. 

2  Dr.  W.  Hesse,  Anleitung  zur  Bestimmung  der  Kohlensaure  in 
der  Luft,  nebst  einer  Beschreibung  des  hierzu  nothigen  Apparatesj 
Eulenberg's  Vierteljahrsschr.  /.  gerichtl.  Medicin  und  offentl.  Sani- 
tatswesen,  N.F.  xxxi.  2. 


GAS    ANALYSIS 


PART  III 


placed  by  water  as  long  as  there  is  material  in  excess 
to  saturate  the  water. 

"  2.  A  bottle  containing  dilute  baryta  water.  The 
bottle  is  provided  with  a  small  absorption  flask  con- 
taining pumice-stone  saturated  with  caustic  potash, 
for  freeing  the  entering  air  from  carbon  dioxide 
(Fig.  99).  This  dilute  baryta  water  is  made  by  add- 
ing about  30  ccm.  of  concentrated  barium  hydroxide 


FIG.  99. 


solution  to  1  liter  of  water,  or  directly  by  dissolv- 
ing 1.7  g.  of  a  mixture  of  barium  hydroxide  and 
barium  chloride  (20  :  1)  in  1  liter  of  distilled  water. 

"  3.  A  solution  of  oxalic  acid  containing  5.6325  g. 
of  crystallised  oxalic  acid  in  1  liter  of  water.  1  ccm. 
=  1  ccm.  CO2. 

"  4.  A  solution  of  phenol-phthalein,  1  part  in  250 
parts  of  alcohol. 


CHAP,  vii      ANALYSIS   OF  ATMOSPHERIC   AIR  339 

"i?.    The  portable  apparatus  comprises  — 

"1.  Five  thick- walled  conical  Erlenmayer  flasks 
of  |,  J,  ^,  j1^,  and  y1^  liter  capacity,  and  supplied  with 
well-fitting,  double-bore  rubber  stoppers.  The  point 
to  which  the  rubber  stopper  reaches  is  marked  on 
the  first  four  flasks,  and  their  capacity  up  to  this 
mark  is  written  on  the  outside  of  each  flask  with  a 
diamond.  The  openings  of  the  stoppers  of  these 
four  flasks  are  closed  with  pieces  of  glass  rod  from  3 
to  5  cm.  long.  These  rods  are  well  rounded  at  the 
lower  ends,  the  upper  ends  being  widened  like  a  but- 
ton. 

"2.    A  thick-walled  10  ccm.  pipette. 

"3.  A  glass  stopcock  burette  holding  from  10  to 
15  ccm.,  graduated  in  tenths,  and  having  a  tip  7  to 
10  ccm.  long. 

"4.  A  300  ccm.  flask  provided  with  a  small  guard 
bottle,  as  in  A  2,  and  filled  with  dilute  baryta  water. 
This  is  filled  in  the  laboratory  by  connecting  it  with 
the  large  reserve  bottle  containing  dilute  baryta 
water,  and  driving  the  solution  over  through  the 
siphon.  Before  beginning  the  experiment  a  few 
drops  of  a  solution  of  rosolic  acid  are  added  to  the 
barium  hydroxide  solution.  The  fainter  the  colour 
the  sharper  is  the  reaction,  but  the  colour  must  not 
be  so  faint  as  to  be  indistinct.  The  proper  colora- 
tion will  last  for  about  three  days ;  it  is  then  so  in- 
distinct that  a  few  drops  of  rosolic  acid  must  again 
be  added. 

"5.  A  250  ccm.  bottle  filled  with  dilute  oxalic 
acid.  This  is  prepared  by  bringing  25  ccm.  of  the 
standardised  oxalic  acid  into  the  250  ccm.  flask,  and 
then  filling  the  flask  to  the  mark  with  water. 


340  GAS   ANALYSIS  PART  in 

"  6.    A  thermometer. 

"  7.    A  barometer  (a  small  aneroid). 

"The  amounts  of  solutions  here  given  for  the 
portable  apparatus  are  sufficient  for  thirty  separate 
determinations  ;  in  other  words,  at  least  ten  analyses, 
including  a  control  determination  each  time  and  the 
standardising  of  the  solution,  can  be  made  with  the 
above  quantities. 

"  Each  determination  of  carbon  dioxide  by  Hesse's 
method  is  a  double  one,  the  two  determinations 
being  made  with  volumes  of  air  of  different  size. 
Accordingly,  flasks  of  J  and  ^,  or  J  and  J,  or  -^  and 
•j1^-  liter  capacity  are  used  for  taking  the  samples  of 
air,  the  sizes  of  the  flasks  chosen  depending  upon 
whether  a  smaller  or  a  larger  amount  of  carbon  diox- 
ide in  the  air  is  to  be  expected.  The  samples  are 
taken  by  completely  filling  the  flasks  at  the  place 
where  the  air  is  to  be  examined  with  water  which 
has  the  temperature  of  the  place,  and  then  emptying 
the  flasks  and  rinsing  them  with  distilled  water.  In 
this  operation  care  must  be  taken  that  the  flask  is 
not  warmed  by  the  hand,  and  that  no  air  exhaled  by 
the  operator  enters  the  flask. 

"  To  absorb  the  carbon  dioxide,  the  10  ccm.  pi- 
pette is  put  through  one  of  the  openings  of  a  stop- 
per fitting  the  flask,  its  end  is  inserted  in  the  rubber 
tube  of  the  supply  flask,  and  the  pipette  is  rinsed 
with  a  little  barium  hydroxide  solution  drawn  up 
into  it.  The  pipette  is  now  filled  to  the  zero  mark 
by  suction,  and  the  stopper  through  which  it  passes 
is  inserted  in  the  neck  of  the  flask  containing  the 
sample  of  air.  The  barium  hydroxide  is  now  run 
into  the  flask,  the  second  opening  of  the  stopper 


CHAP,  vii      ANALYSIS  OF  ATMOSPHERIC  AIR  341 

being  obstructed  with  the  finger  or  a  glass  rod  to 
such  an  extent  that  the  displaced  air  can  just  escape. 
The  glass  rod  is  then  pushed  into  place,  and  the 
pipette  is  freed  from  the  few  drops  of  solution  ad- 
hering to  it  by  closing  it  at  the  top  and  warming  it 
with  the  hand.  The  pipette  is  then  drawn  out  of 
the  stopper,  and  the  second  opening  is  closed  with  a 
glass  rod.  The  same  proceeding  is  repeated  with  a 
second  flask  of  different  capacity.  The  two  flasks 
are  allowed  to  stand  for  some  time  .with  occasional 
shaking,  and  in  the  meantime  the  strength  of  the 
baryta  water  is  determined. 

"  The  strength  of  the  baryta  water  is  determined 
by  putting  into  the  small  flask  of  -^  liter  capacity 
nearly  as  much  standardised  oxalic  acid  solution  as 
will  be  required  in  the  titration,  and  then  running  in 
10  ccm.  of  the  solution  of  barium  hydroxide.  The 
solution  is  then  neutralised  by  slowly  running  in  more 
oxalic  acid,  and  the  total  oxalic  acid  necessary  is  thus 
determined.  By  proceeding  in  this  manner  a  very 
exact  standardising  of  the  solution  is  possible,  even  in 
an  atmosphere  containing  much  carbon  dioxide,  be- 
cause the  solution  is  never  strongly  alkaline  enough 
to  absorb  appreciable  amounts  of  carbon  dioxide  from 
the  air. 

"  The  baryta  water  which  has  been  shaken  with  the 
air  is  titrated  without  previously  removing  the  barium 
carbonate.  The  titration  is  made  as  follows  :  — 

"  Remove  the  glass  rod  from  one  of  the  openings 
in  the  stopper,  and  immediately  insert  the  tip  of  the 
burette  which  has  already  been  filled  with  oxalic 
acid  solution.  The  tip  of  the  burette  should  reach 
as  far  as  possible  into  the  flask  (Fig.  100).  Open 


342 


GAS  ANALYSIS 


PART  IH 


the  stopcock  of  the  burette  and  allow  the  oxalic  acid 
to  enter  rapidly  at  first,  but  at  the  last  only  drop  by 
drop.  If  the  increased  pressure  resulting  inside  the 
flask  checks  the  flow  of  liquid  from  the  burette,  this 

pressure  is  removed  by  lift- 
ing the  glass  stopper  for  a 
moment.  When  the  solu- 
tion is  neutral,  i.e.  when 
it  is  completely  decoloured, 
the  height  of  the  solution 
in  the  burette  is  noted, 
and  the  contents  of  the 
second  flask  is  titrated  in 
the  same  manner. 

"  It  is  clear  that  when  the 
amount  of  carbon  dioxide 
present  is  small,  the  accu- 
racy of  the  determination 
is  increased  by  using  larger 
volumes  of  air.  For  this 
reason  Hesse  uses  a  flask 
of  ^  or  1  liter  capacity 
whenever  the  carbon  di- 
oxide is  probably  below 
the  limit  for  dwelling- 
rooms,  as,  for  example,  in 
the  open  air.  He  also  uses  three  sizes  when  great 
accuracy  is  desired.  Of  course  sufficient  barium 
hydroxide  solution  must  be  taken  to  insure  its  being 
present  in  excess  up  to  the  end  of  the  operation.  The 
small  amount  of  carbon  dioxide  which  the  baryta 
water  takes  up  from  the  air  that  it  displaces  when 
running  into  the  flask  may  be  disregarded. 


FIG.  100. 


CHAP,  vii      ANALYSIS   OF   ATMOSPHERIC   AIR 


343 


"  In  using  this  method  for  determining  the  carbon 
dioxide  present  in  the  soil  or  in  walls,  Hesse  employs 
the  apparatus  shown  in  Fig.  101.  The  air  in  the  soil 
is  drawn  through  the  flask  by  means  of  a  rubber 
pump ;  the  glass  tubes  are  then  removed,  and  the 


FIG.  101. 

openings  in  the  stopper  are  closed  with 
glass  rods.  The  titration  is  made  as 
before  described,  but  more  concentrated 
reagents  are  required.  In  examining 
the  air  of  graves,  Hesse  used  a  solution 
of  barium  hydroxide  ten  times  as  strong 
as  that  previously  given  (10  ccm.  = 
about  10  ccm.  oxalic  acid  solution  A3  = 
10  ccm.  CO2). 

"  In  calculating  the  analysis,  the  volume  of  air 
taken  is  reduced  to  normal  pressure  and  temperature 
so  that  correct  comparisons  may  be  made.  This  cal- 
culation takes  considerable  time,  and  to  Hesse  belongs 
the  merit  of  having  compiled  a  table l  giving  the 

1  Dr.  med.  Walter  Hesse,  Tdbellen  zur  Reduction  eines  Gas- 
volumes  auf  0°  Temperatur  und  760  mm.  Luftdruck.  Braun- 
schweig, 1879. 


344  GAS  ANALYSIS  PART  in 

figures   by   which  the   amounts   of   carbon   dioxide 
found  in  the  uncorrected  gas  volume  are  to  be  mul- 
tiplied.    The  table  contains  for  each  degree  of  tem- 
perature the  multiplier  for  any  barometric  pressure. 
"  Example  — 

V  =  223  ccm.,  t  =  19°,  b  =  739  mm. ; 

the  titration  of  the  baryta  water  gave  10  ccm. 
baryta  water  =  11. 5  ccm.  oxalic  acid,  and  in  the 
experiment  6.2  ccm.  oxalic  acid  was  used.  Hence 
the  amount  of  carbon  dioxide  which  had  already 
united  with  the  barium  hydroxide  was  equivalent  to 
11.5  —  6.2  =  5.3  ccm.  oxalic  acid,  corresponding  to 
0.53  ccm.  CO2,  and  we  have  the  proportion  — 

[223  -  10]  i  or  213  :  0.53  =  1000  :  x, 
x=  2.49  ccm.  (in  unreduced  liter). 

"The  multiplier  corresponding  to  this  tempera- 
ture and  barometric  pressure  is  1.100;  hence  in  the 
reduced  liter  there  are  2.49x1.100  =  2.7  ccm.  or 
in  the  air  examined  2.7  parts  per  thousand  of  CO2 
present. 

"The  whole  operation,  including  the  control  de- 
termination and  the  calculation,  may  be  completed  in 
from  a  quarter  to  half  an  hour.  Hesse  recommends 
that  the  results  be  put  down  in  the  form  shown  in 
the  following  table.  The  examples  given  show  how 
well  the  results  agree  even  under  the  most  varied 
modifications.  The  calculations  of  the  results  given 

1  Subtraction  from  the  volume  to  allow  for  the  barium  hydrox- 
ide solution  which  was  run  in. 


CHAP,  vii      ANALYSIS   OF  ATMOSPHERIC   AIR 


345 


M 

After  a  two- 
hour  ses- 
sion 

Titrated  in 
a  room  at 
21° 

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346  GAS  ANALYSIS 


PART  III 


in  the  table l  were  made  with  the  aid  of  logarithms, 
but  are  carried  out  to  only  one  decimal." 

PETTERSSON'S  METHOD 

A  very  exact  method  for  the  determination  of 
carbon  dioxide  and  water  vapour  has  been  devised 
by  Pettersson.2  He  describes  the  method  as  fol- 
lows: — 

"  With  the  apparatus  shown  in  Fig.  102  an  accu- 
rate determination  of  the  water  and  carbon  dioxide 
in  the  air  may  be  quickly  made. 

"J.  is  a  pipette  with  a  graduated  tube.  It  is 
joined  at  the  top,  by  narrow  but  not  capillary  glass 
tubes,  to  the  two  reservoirs  B  and  0.  B  is  loosely 
filled  with  glass-wool  and  phosphorus  pentoxide,  and 
0  with  glass-wool  and  soda-lime.  For  the  sake  of 
clearness  the  connecting  tubes  are  drawn  in  the  fig- 
ure much  wider  than  they  really  are.  The  remainder 
of  the  apparatus,  however,  is  shown  so  far  as  possible 
in  the  proper  proportions.  The  whole  system  of  the 
three  glass  reservoirs  is  immersed  in  a  vessel  of 

1  In  the  table  — 

h  =  time  of  day. 
t  —  temperature  centigrade. 

b  =  barometric  pressure  in  millimeters  of  mercury. 
V  =  volume  of  glass  flask. 
BW  =  cubic  centimeters  of  baryta  water  used. 

Titer  9.35  means  that  10  ccm.  barium  hy- 
droxide solution  =9. 35  ccm.  oxalic  acid  = 
0.935  ccm.  CO2. 

Oxal.  =  cubic  centimeters  of  oxalic  acid  solution  used. 
C02  unreduced  =  carbon  dioxide  in  cubic  centimeters  in  the  un- 
reduced liter. 

CC>2  reduced  =  carbon  dioxide  in  the  reduced  liter  =  parts  per 
thousand. 

2  Zeitschrift  fur  analytische  Chemie,  25,  467-484. 


CHAP,  vii       ANALYSIS  OF  ATMOSPHERIC   AIR 

r  T 


347 


water  in  which 
the  temperature 
is  kept  uniform, 
but  of  course 
not  constant,  by 
means  of  a 
stirrer.  The 
handles  of  the 
stirrer  are  shown 
in  Fig.  102,  r  r, 
and  the  disk  in 
Fig.  103,  R. 

"  The  analysis 
consists  in  meas- 
uring a  sample 
of  air  in  the 
pipette  A,  then 
driving  it  over 
into  the  drying 
cylinder  B, 
bringing  it  back 
into  A,  and  meas- 
uring the  de- 
crease of  volume 
caused  by  the 
drying.  Then  in 
similar  manner 


FIG.  103. 


FIG.  102. 


348  GAS  ANALYSIS  PART  in 

the  carbon  dioxide  present  in  the  dried  air  is  absorbed 
in  (7,  and  the  decrease  of  volume  is  measured  in  A. 
The  analysis  thus  comprises  two  different  kinds  of 
operations  — 

"  1.  The  driving  back  and  forth  of  the  air  from 
one  vessel  to  another. 

"  2.  The  adjusting  of  the  mercury  level  in  the 
graduated  tube,  and  the  measuring  of  the  volume  of 
the  air  enclosed  in  A  after  each  operation. 

"  1.  The  air  to  be  examined  is  taken  directly  from 
the  room  or  from  the  free  atmosphere  by  means  of 
a  glass  tube  connected  with  the  upper  end  of  the 
pipette  and  passing  out  into  the  open  air.  The 
pipette  in  the  beginning  is  entirely  filled  with  mer- 
cury, and  the  air  is  drawn  in  by  allowing  this  mer- 
cury to  run  out  until  it  stands  about  at  the  lower 
zero  mark  of  the  graduated  tube.  The  stopcock  X 
is  then  closed,  and  the  level  of  the  mercury  is  accu- 
rately adjusted  with  the  screw/,  which,  by  means  of 
a  brass  plate,  compresses  the  rubber  tube  joining  the 
stopcock  X  with  the  graduated  tube.  If  the  level  in 
the  graduated  tube  has  been  brought  at  the  begin- 
ning to  nearly  the  proper  position,  a  slight  turning 
of  the  screw  suffices  for  an  accurate  adjustment  of 
the  mercury,  The  adjustment  may  be  made  still 
sharper  by  using  a  magnifying  glass.  During  this 
operation  there  is  considerable  pressure  in  the  rub- 
ber tube  upon  which  the  screw  acts.  For  this  rea- 
son a  piece  of  thick-walled  rubber  tubing  is  chosen, 
and,  after  it  has  been  placed  in  position,  an  envelope 
of  strong  silk  is  sewed  around  it.  The  rubber  will 
then  hold  for  an  unlimited  time  without  bursting. 

"  When  the  pipette  has  been  filled  with  air,  S,  e,  a, 


CHAP,  vii      ANALYSIS  OF  ATMOSPHERIC  AIR  349 

and  ft  are  opened  so  that  there  may  be  the  same 
pressure  throughout  the  apparatus,  and  the  stirrer  is 
set  in  motion  so  that  all  parts  of  the  apparatus  may 
take  the  same  temperature.  The  small  drop  of  liquid 
x  in  the  differential  manometer  will  then  come  to 
rest  opposite  one  of  the  marks  on  the  little  scale. 
This  position  must  be  accurately  observed  with  the 
magnifier,  because  in  all  subsequent  operations  the 
drop  must  be  brought  to  exactly  the  same  position 
before  a  reading  of  the  volumes  is  taken.  After  one 
is  convinced  that  all  differences  of  temperature  and 
pressure  have  been  equalised,  7,  S,  and  /3  are  closed, 
e  is  left  open.  X  is  now  opened,  and  the  mercury 
reservoir  is  raised  by  means  of  a  sliding  arrange- 
ment. The  pipette  A  gradually  fills  with  mercury, 
and  the  air  is  driven  over  into  B.  As  B  was  full  of 
dry  air  in  the  beginning,  the  pressure  in  it  becomes 
quite  high,  and  although  in  my  apparatus  the  volume 
of  B  is  about  one-third  larger  than  A  (which  con- 
tains exactly  100  ccm.),  the  movable  mercury  reser- 
voir must  be  raised  nearly  130  cm.  in  order  to  raise 
the  mercury  in  the  pipette  from  the  lower  zero  mark 
to  the  T  of  the  connecting  tubes  at  the  top,  and  thus 
drive  all  of  the  air  in  A  over  into  B. 

"  As  is  well  known,  phosphorus  pentoxide  absorbs 
the  moisture  of  the  air  rapidly  and  completely.1 
On  that  account  it  will  perhaps  be  surprising  that, 
according  to  my  experience,  the  air  entering  B  must 
be  left  for  ten  to  twenty  minutes  in  contact  with  the 
pentoxide  in  order  to  remove  every  trace  of  mois- 
ture. The  result  may  be  easily  controlled  by  again 

1  See  the  work  of  Fresenius  in  Zeitschrift  f.  analyt.  Chemie,  4, 
177;  also  Dibbits,  ibid.,  15,  121. 


350  GAS   ANALYSIS  PART  in 

passing  the  dried  air  into  B,  and  then  measuring  the 
decrease  in  volume  resulting  from  the  second  absorp- 
tion. To  be  sure,  the  greater  part  of  the  moisture 
is  absorbed  in  a  few  minutes,  but  the  traces  are 
removed  from  the  air  only  after  it  has  stood  for 
some  time  in  the  drying  cylinder  B.  The  apparent 
difference  between  earlier  experiments  and  my  own 
experience  concerning  the  rapidity  with  which  phos- 
phorus pentoxide  completely  absorbs  moisture  finds 
an  easy  explanation  in  the  different  conditions  under 
which  we  operated.  Up  to  the  present  time  experi- 
menters have  determined  the  rapidity  with  which 
a  current  of  air  passing  over  phosphorus  pentoxide 
will  lose  the  moisture  which  it  contains.  In  my  ex- 
periments a  volume  of  air  at  rest  is  exposed  to  the 
dehydrating  action  of  the  pentoxide,  and  it  is  natu- 
ral that  a  longer  time  should  be  necessary  for  the 
absorption  to  become  complete. 

"  The  absorption  of  the  carbon  dioxide  in  Q  is  car- 
ried out  in  a  similar  manner.  The  stopcocks  e  and  a 
must  be  closed  and  S  opened:  7  and  /JL  remain  closed 
during  the  whole  analysis.  The  carbon  dioxide  is 
absorbed  much  more  rapidly  by  the  soda-lime  than 
is  the  aqueous  vapour  by  the  phosphorus  pentoxide. 
Ten  minutes  are  usually  sufficient  for  removing  the 
last  traces  of  the  carbon  dioxide,  so  that  when  the 
operation  is  repeated  no  further  decrease  in  volume 
can  be  observed  in  the  graduated  tube.  Since  soda- 
lime  loses  one  molecule  of  water  for  every  molecule 
of  carbon  dioxide  which  it  absorbs,  I  naturally  ex- 
pected that  the  air  coming  from  0  after  having  been 
freed  from  carbon  dioxide  would  contain  a  slight 
amount  of  moisture,  and  that  this  moisture  would 


CHAP,  vii      ANALYSIS   OF  ATMOSPHERIC   AIR  351 

have  to  be  removed  by  repeated  absorption  in  B. 
To  my  surprise,  however,  the  air  proved  to  be  com- 
pletely dry  after  the  absorption  of  carbon  dioxide, 
and  although  I  passed  the  air  into  B  after  each 
determination  of  carbon  dioxide,  I  was  able  to  detect 
in  only  a  few  experiments  a  decrease  of  volume  of 
about  0.003  or  0.004  per  cent.  This  decrease  was  of 
course  brought  into  the  calculation,  but  it  may  have 
been  accidental,  since  the  average  uncertainty  in  this 
determination  of  carbon  dioxide  amounts  to  about 
0.002  per  cent.  I  would  here  state  that  I  use  in  0 
soda-lime  which  has  been  thoroughly  dried  and 
heated,  and  that  the  quantity  of  carbon  dioxide 
which  is  absorbed  in  each  experiment  (especially  in 
the  analyses  of  air  from  the  streets  of  Stockholm, 
where  the  carbon  dioxide  amounts  to  only  0.039  to 
0.059  per  cent)  is  exceedingly  small  in  comparison 
with  the  large  amount  of  absorbent  which  certainly 
contains  a  great  deal  of  lime.  I  have  had  the  same 
experience  with  two  different  pieces  of  apparatus, 
yet  I  do  not  mean  to  assert  that  every  soda-lime  (a 
product  which,  as  is  known,  is  prepared  in  very  dif- 
ferent ways)  would  have  the  same  action,  or  that  the 
contents  of  the  reservoir  O  in  my  apparatus  will 
hold  back  the  moisture  as  completely  after  several 
hundred  analyses  as  it  does  now.  It  facilitates  and 
shortens  the  analysis  if  the  sample  of  air  need  be  dried 
but  once ;  and  since  it  has  turned  out,  although  con- 
trary to  my  expectation,  that  the  moisture  formed 
in  the  absorption  of  the  carbon  dioxide  can  be  taken 
up  completely  by  the  soda-lime  itself,  I  would  advise 
that  some  quick -lime  be  mixed  with  the  soda-lime. 
A  few  control  experiments  will  of  course  best  decide 


352  GAS  ANALYSIS  PART  in 

as  to  whether  or  not  we  can  depend  upon  the  dehy- 
drating action  of  the  soda-lime. 

"2.  I  now  come  to  the  second  kind  of  analytical 
operation,  namely,  the  adjustment  and  the  measur- 
ing of  the  gas  volume.  The  principle  of  this  new 
method  permits  the  measuring  of  the  volume  of 
air,  after  each  absorption,  by  a  direct  reading  of 
the  graduated  tube  without  regard  for  any  changes 
of  temperature  and  pressure  which  may  have  taken 
place  during  the  experiment.  Variations  in  the 
pressure  of  the  external  atmosphere  cannot  affect  the 
measurements,  because  the  stopcocks  7  and  \L  remain 
closed  during  the  whole  analysis.  The  temperature 
of  the  water  surrounding  A,  B,  and  0  is  kept  uniform 
by  stirring.  To  be  sure,  the  temperature  changes 
constantly,  but  the  change  is  gradual,  and  the  press- 
ure in  all  three  reservoirs,  A,  B,  and  (7,  rises  or 
falls  to  the  same  extent.  Two  of  these  reservoirs 
are  always  in  communication  with  each  other;  the 
third  is,  however,  cut  off  from  the  others.  For  ex- 
ample, during  the  determination  of  water,  A  and  B 
communicate  through  the  stopcock  e,  and  of  them- 
selves form  a  distinct  system ;  the  air  in  0  is  sepa- 
rated from  them  from  the  beginning  of  the  experiment 
by  the  closed  stopcock  8.  The  operations  above 
described  are  now  carried  out  with  the  air  in  A,  the 
air  being  passed  into  B,  then  brought  back  in  dry 
condition  into  J.,  and  the  level  of  the  confining 
mercury  so  adjusted  by  the  eye  that  the  air  in  A 
has  approximately  its  original  pressure.  Upon  now 
opening  the  stopcock  fS,  the  little  index  x  in  the 
differential  manometer  moves  toward  the  right  or 
left,  according  to  whether  the  mercury  in  the  gradu- 


CHAP,  vii      ANALYSIS   OF  ATMOSPHERIC  AIR  353 

ated  tube  stands  too  low  or  too  high.  \  is  closed 
and  the  screw  /  is  turned  until  x  has  taken  precisely 
the  same  position  which  it  had  at  the  beginning. 
It  is  obvious  that  the  pressure  in  A  and  B  is  now 
identical  with  the  pressure  prevailing  in  (7,  because 
the  air  in  (7,  the  stopcock  a  being  open,  acts  upon 
the  left  side  of  the  drop  of  liquid  z,  and  the  slightest 
difference  in  pressure  would  cause  a  great  displace- 
ment of  the  drop  toward  one  side  or  the  other.  The 
sensitiveness  is,  in  fact,  so  great  that  a  very  slight 
turning  of  /,  which  would  increase  or  diminish  the 
volume  of  air  in  A  by  0.002  ccm.,  moves  the  index 
1  mm.  to  the  right  or  left.  The  nature  of  the  drop 
of  liquid  #,  which  plays  the  part  of  an  index,  has 
a  great  influence  upon  the  size  of  the  deviation. 
I  prefer  to  use  a  drop  of  concentrated  sulphuric  acid 
coloured  with  indigo  blue :  the  drop,  in  order  to  be 
easily  movable,  occupies  only  3  to  4  mm.  of  the  length 
of  the  manometer  tube.  The  tube  is  slightly  bent,  so 
that  the  drop  tends  of  itself  to  take  a  position  in  the 
middle.  The  width  of  the  manometer  tube  has  but 
little  influence,  provided  that  it  is  not  too  narrow. 
An  index  of  high-boiling  petroleum  is  even  more 
sensitive  than  the  sulphuric  acid.  Since  the  sensi- 
tiveness for  slight  differences  of  pressure  is  so  great, 
the  stopcocks  13  and  a  must  be  opened  very  carefully, 
to  avoid  driving  the  drop  out  of  the  manometer  tube. 
It  is  best  never  to  open  both  a  and  ft  at  once,  but 
to  keep  one  stopcock  closed  until  the  level  in  the 
graduated  tube  has  been  brought  into  approximately 
correct  adjustment.  If  the  operation  is  thus  carried 
out  an  analysis  will  never  be  lost. 

"  It  follows  from  what  has  been  said  that  the  method 

2A 


354  GAS   ANALYSIS  PART  in 

in  reality  consists  in  bringing  the  sample  of  air  after 
each  operation  under  exactly  the  same  relations  of 
pressure  and  temperature  as  prevail  in  the  second 
part  of  the  system.  For  example,  there  is  present 
in  all  parts  of  the  apparatus  at  the  beginning  of  the 
analysis  a  temperature  t  and  a  pressure  p.  During 
the  absorption  of  the  water  the  air  in  0  is  at  rest 
and  is  separated  from  A  and  B.  Its  temperature 
changes  gradually  from  t  to  tv  the  pressure  from  p 
to  pr  After  the  absorption  of  water,  the  dry  air  in 
A  (and  also  that  in  B)  is  brought  to  the  same  press- 
ure pl  with  the  help  of  the  screw  /  and  the  index 
x  in  the  manner  already  described.  The  temperature 
is  of  course  tv  Hence  the  determination  in  the  grad- 
uated tube  of  the  decrease  in  volume  is  made  under 
another  pressure  and  another  temperature  from  those 
at  the  beginning.  Nevertheless  the  decrease  in  vol- 
ume gives  directly  and  without  correction  the  volume 
per  cent  of  the  moisture  in  the  air,  just  as  though  the 
dried  air  were  measured  under  constant  temperature 
and  constant  pressure.  It  is  easy  to  understand  that  if 
the  temperature  in  the  water  jacket,  and  consequently 
in  the  whole  apparatus,  were  brought  back  to  £,  the 
air  would  again  have  the  original  pressure  p  without 
any  change  whatever  being  necessary  in  the  adjust- 
ment of  the  index  or  of  the  level  of  the  mercury  in 
the  graduated  tube.  The  glass  vessels  A  and  B  on 
the  one  hand,  and  0  on  the  other,  as  well  as  the 
air  contained  in  them,  change  their  volumes  in  the 
same  proportion.  Hence  in  this  method  the  changes 
of  temperature  during  the  analysis  eliminate  them- 
selves, and  the  determinations  give  directly  (due 
regard  being  of  course  given  to  the  table  of  calibra- 


CHAP,  vii      ANALYSIS   OF  ATMOSPHERIC   AIR  355 

tion)   the  volume    per  cents   of   water  and   carbon 
dioxide. 

"  A  few  remarks  may  here  be  in  place.  The  influ- 
ence of  variations  of  temperature  upon  the  air  vol- 
umes which  are  separated  from  each  other  —  A  and 
B  from  O  in  the  determination  of  moisture,  and  in 
the  carbon  dioxide  determination  A  and  O  from  B  — 
is  reciprocally  compensated  by  the  uniform  expansion 
of  the  glass  vessels  and  the  dry  gases.  If  after  the 
index  has  been  brought  to  rest  the  apparatus  is  left 
with  the  stopcocks  a  and  ft  open  and  either  8  or  e 
closed,  the  index  does  not  move  although  the  tem- 
perature of  the  water  may  slowly  change  several 
tenths  of  a  degree.  Only  when  the  change  of  tem- 
perature amounts  to  whole  degrees  is  there  seen  a 
tendency  of  the  index  to  move  toward  the  right  or 
left.  This  is  caused  by  the  unequal  expansion  of 
the  solid  phosphorus  pentoxide  in  B  and  the  soda- 
lime  in  (7.  The  expansion  of  these  substances  is  for 
the  most  part  self-compensating,  but  it  is  never  com- 
pletely so,  and  the  influence  of  this  source  of  error  is 
manifested,  in  experiments  which  last  quite  long,  as 
a  slight  uncertainty  amounting  to  some  millionths  of 
the  total  volume.  This  degree  of  accuracy  has  never 
been  attained  by  any  of  the  earlier  methods  for  de- 
termining the  moisture  of  the  atmosphere,  so  that  the 
slight  uncertainty  mentioned  above  may  be  wholly 
disregarded  when  the  apparatus  is  used  as  a  hygrom- 
eter. In  the  determination  of  the  atmospheric 
carbon  dioxide,  however,  it  is  desirable  that  this 
difficulty  be  removed.  The  defect  in  the  compen- 
sation could  be  met  by  allowing  some  mercury  to 
enter  B  or  0  until  the  expansion  of  the  air  in  both 


356  GAS  ANALYSIS  PART  in 

was  equal.  I  have  not  tried  this  expedient  with  my 
apparatus,  because  the  following  procedure  accom- 
plished the  end. 

"When  the  volume  of  the  dried  air  has  been  meas- 
ured in  A,  I  do  not  proceed  at  once  to  the  determina- 
tion of  carbon  dioxide  in  the  same  volume  of  air. 
After  the  absorption  of  water  the  volume 
of  the  mercury  usually  stands  in  the  wider 
part  of  the  graduated  tube  (Fig.  104).  In- 
stead of  making  the  reading  after  the  carbon 
dioxide  absorption  upon  the  same  portion 
of  the  scale,  where  1  mm.  =  0.01116  com.,  I 
prefer  to  open  the  stopcock  /j,  and  to  allow 
a  small  volume  of  dry  atmospheric  air  to 
enter  A  through  g  and  B  until  the  mercury 
again  stands  at  the  lower  zero  mark  of  the 
graduated  tube.  Since  the  pipette  with  the 
graduated  tube  holds  exactly  100  ccm.,  it 
now  contains  100  ccm.  of  dry  air  under 
atmospheric  pressure.  7,  e,  a,  and  /3  are 
now  opened  for  a  couple  of  seconds  to  allow 
the  air  in  C  also  to  assume  the  pressure 
of  the  atmosphere.  Then  7,  a,  e,  and  p 
are  closed.  8  is  left  open  and  the  absorp- 
FlG'  °  '  tion  of  the  carbon  dioxide  is  brought  about 
in  ten  minutes  by  driving  the  air  from  A  into  0. 
The  decrease  in  volume  is  then  measured  in  the 
lower  narrow  part  of  the  graduated  tube  where 
1  mm.  =  0.00199  ccm.  In  such  a  short  time  (the 
determination  of  the  carbon  dioxide  does  not  take 
half  an  hour)  the  temperature  will  not  change  enough 
to  make  the  error  in  compensation  amount  to  more 
than  about  0.002  per  cent.  It  is  best,  however,  in 


CHAP,  vii       ANALYSIS  OF  ATMOSPHERIC  AIR  357 

determinations  of  atmospheric  carbon  dioxide  which 
call  for  great  exactness  to  keep  the  temperature  of 
the  room  relatively  constant.1  In  analysing  the  air 
of  rooms,  where  accuracy  to  the  millionths  need  not 
be  striven  for,  the  work  may  be  carried  on  in  a  newly 
heated  room  quite  near  the  stove  without  any  con- 
siderable errors  resulting.  One  should,  however, 
seek  to  avoid  the  action  of  direct  radiation  from  a 
fire  or  from  the  sun.  For  the  hygienic  examination 
of  the  air  of  rooms,  as  well  as  for  the  hygrometric 
determination  of  the  moisture  of  the  atmosphere, 
where  the  accuracy  demanded  is  not  greater  than 
0.05  per  cent,  I  have  a  small  apparatus  in  which  the 
pipette  A  holds  only  18  ccm.,  the  other  parts  of  the 
apparatus  being  correspondingly  small.  This  appa- 
ratus can  be  enclosed  in  a  small  wooden  box  60  cm. 
high,  and  may  be  carried  in  the  hand.  Here  also  the 
absorption  of  the  carbon  dioxide  is  made  with  dry 
soda-lime,  but  the  absorption  of  moisture  is  carried 
out  in  an  Orsat  tube  filled  with  concentrated  sul- 
phuric acid.  The  compensation  of  the  temperature 
variations  is  based  upon  the  principle  stated  below. 
In  this  apparatus  also  the  graduated  tube  has  a  wide 
and  a  narrow  portion,  but  the  wider  part  is  below  and 
serves  for  the  determination  of  water,  and  the  carbon 
lioxide  determination  is  made  in  the  narrow  part  of 
the  tube  which  stands  above. 
"  In  working  with  the  larger  apparatus,  one  finds 

1  Do  not  seek  to  obtain  a  constant  temperature  in  the  apparatus 
bp  pouring  in  warm  or  cold  water.  Every  such  addition  is  a  source 
o.  sudden  variations  of  temperature  which  make  themselves  known 
tfrough  the  oscillations  of  the  index.  The  index  remains  quiet 
oily  when  the  apparatus  is  left  to  itself. 


358  GAS  ANALYSIS  PART  in 

that  the  index  does  not  at  once  come  to  rest  after  a 
determination  of  water  or  carbon  dioxide  has  been 
made,  and  the  mercury  in  the  graduated  tube  prop- 
erly adjusted.  For  from  five  to  ten  or  twelve  minutes 
the  index  slowly  moves,  giving  the  impression  that 
in  the  pipette  and  the  absorption  vessel  communicat- 
ing with  it  —  either  B  or  Q — the  air  is  being  warmed. 
This  is  actually  the  case.  When  the  air  which  has 
been  compressed  in  B  or  C  enters  A  it  expands 
adiabatically  and  becomes  cooler. 

"  Only  after  several  minutes'  standing  is  this  loss 
of  heat  equalised  by  the  water  outside  the  pipette. 
On  this  account  the  water  must  be  stirred,  and  the 
reading  must  not  be  made  until  the  index  has  come 
to  rest.  The  analysis,  which  otherwise  would  take 
probably  less  than  half  an  hour,  is  thus  made  con- 
siderably longer.  For  this  reason,  the  absorption  of 
water  in  the  small  apparatus  for  hygienic  and  hygro- 
metric  determinations  is  made  in  an  Orsat  tube  fused 
on  to  the  apparatus,  the  adiabatic  cooling  being  here 
imperceptible. 

"  When  the  water  is  absorbed  by  a  solid  substance 
it  is  indispensable  that  the  vessel  B  be  previously 
filled  with  the  same  kind  of  dry  air  as  that  to  be 
analysed.  A  should  not  be  filled  with  atmospheric 
air  while  B  contains  the  dry  air  of  the  room,  because, 
for  reasons  easily  seen,  the  determination  of  the  car- 
bon dioxide  would  then  be  inexact.  For  this  reasoi 
B  is  filled  before  the  analysis  with  air  of  the  sama 
nature  as  that  to  be  analysed  later.  This  air  enteis 
B  through  the  tube  g  containing  phosphorus  pen-- 
oxide and  through  the  stopcock  p.  The  air  is  drawn 
in  by  first  filling  the  pipette  A  with  mercury,  ard 


CHAP,  vii       ANALYSIS   OF  ATMOSPHERIC  AIR  359 

then,  having  closed  the  stopcocks  7,  S,  and  ft,  lower- 
ing the  mercury  reservoir.  The  air  enters  B  from 
below  through  a  small  projecting  tube  over  which  a 
U-shaped  tube  is  placed,  and  takes  the  place  of  the 
air  passing  from  B  into  A.  The  operation  must  of 
course  be  repeated  several  times,  especially  when 
samples  of  air  from  very  different  sources  are  suc- 
cessively analysed. 

"  Concerning  the  technical  making  of  the  apparatus 
the  following  may  be  said  :  — 

"  The  three  reservoirs  A,  B,  and  Q  form,  with  the 
connecting  glass  tubes,  a  single  system.  I  order 
them  from  Franz  Miiller,  in  Bonn,  Germany,  who 
furnishes  them  at  low  prices  and  carefully  made.  I 
have  preferred  to  have  A,  B,  and  C  sent  to  me  in 
separate  pieces.  I  myself  then  fill  B  with  phosphorus 
pentoxide  and  O  with  soda-lime,  and  also  calibrate 
the  graduated  tube  of  the  pipette  A.  The  three 
reservoirs  are  then  fastened  with  string  in  the  proper 
position  on  a  thin  board.  At  the  two  places  where 
the  tubes  are  to  be  fused  together  large  holes  are  cut 
in  the  board,  so  that  the  ends  of  the  glass  tubes, 
which  must  be  pushed  close  together,  may  be  reached 
with  the  flame  from  all  sides.  After  first  warming 
them  with  an  alcohol  lamp,  the  glass  tubes  may  be 
easily  and  tightly  fused  together  with  the  help  of  a 
blast-lamp  or  a  small  gas  blow-pipe.  In  this  way  it 
is  easily  possible  without  further  practice  to  put 
together  much  more  complicated  pieces  of  glass  appa- 
ratus. One  might  perhaps  just  as  well  order  from  the 
manufactory  reservoirs  which  are  already  filled  and 
joined  together.  The  ordinary  Geissler  stopcocks 
are  usually  made  with  sufficient  care  to  enable  them 


360  GAS   ANALYSIS      ,  PART  in 

to  withstand  the  pressure  arising  in  the  apparatus.1 
But  since  the  slightest  error  makes  the  whole  appa- 
ratus useless,  Miiller  has  made  stopcocks  of  longer 
and  less  conical  surface  ;  these  answer  the 
purpose  admirably.  The  tube  connecting 
the  glass  stopcock  X  with  the  movable 
mercury  reservoir  has  to  withstand  a  high 
internal  pressure.  For  this  purpose  I  use 
an  ordinary  rubber  tube  not  too  thin- 
walled  —  either  red  or  black  rubber  is  the 
best  —  and  surround  it  with  a  spiral  of 
flexible  copper  wire,  as  shown  in  Fig. 
105.  Such  tubes  are  very  easy  to  make, 
FIG.  105.  anci  they  last  for  several  years  even  when 
they  have  to  withstand  an  internal  pressure  of  more 
than  one  atmosphere.  The  glass  connecting  tubes 
and  stopcocks  should  have  openings  not  less  than 
1  mm.  in  diameter. 

"  The  moisture  in  the  atmosphere  is  usually  deter- 
mined with  psychrometers  and  from  the  readings  of 
the  dry  and  wet  thermometer,  —  the  psychrometrical 
difference,  —  and  with  the  help  of  empirically  derived 
formulas  and  tables  the  result  is  expressed  as  the 
moisture  pressure  in  millimeters  of  mercury.  Since 
determinations  of  moisture  can  be  easily  and  accu- 
rately carried  out  with  my  apparatus,  I  have  made  a 
number  of  parallel  researches  with  psychrometer  ther- 
mometers from  the  Central  Meteorological  Station. 
The  agreement  is  generally  good  when  the  tempera- 
ture of  the  air  is  not  too  low.  In  this  case  the  psy- 
chrometric  method,  as  is  well  known,  cannot  be  used, 
because  the  differences  become  too  minute  or  at  times 

1 N.  B.  —  If  they  are  not  too  conical  in  form. 


CHAP,  vii      ANALYSIS   OF   ATMOSPHERIC   AIR  361 

negative.  On  this  account  when  scientific  expedi- 
tions have  spent  the  winter  in  arctic  regions  they 
have  usually  been  obliged  to  give  up  the  determina- 
tion of  the  atmospheric  moisture.  I  hope  that  in 
such  cases,  and  generally  in  meteorological  determi- 
nations of  the  moisture  in  the  air,  the  apparatus 
described  above,  but  of  very  much  smaller  dimensions, 
may  do  good  service.  The  most  natural  and  simple 
method  for  determining  the  moisture  of  the  atmos- 
phere is  to  directly  ascertain  the  volume  per  cent  of 
the  aqueous  gas  or  vapour  without  necessity  of  cor- 
rections for  pressure  or  temperature.  It  is  these 
corrections  probably  which  deter  chemists  from  using 
the  other  absorption  methods  for  the  determination 
of  atmospheric  moisture  (Schwackhofer's  apparatus, 
etc.). 

"  The  determination  of  the  carbon  dioxide  in  air 
is  in  itself  so  difficult  that  one  must  be  prepared  to 
use  either  relatively  large  apparatus  or  an  incon- 
venient equipment  and  method  of  work.  Instead  of 
giving  a  resume  of  the  many  methods  and  proposals 
in  this  line,  I  will  call  attention  only  to  the  experience 
of  Professor  W.  Spring  in  his  well-known  and  ad- 
mirable work  upon  the  determination  of  the  carbon 
dioxide  in  the  air  at  Liittich.  Professor  Spring  care- 
fully tested  all  of  the  methods  in  use,  and  the  only 
method  which  he  found  good  was  the  chemical  deter- 
mination of  carbon  dioxide  with  barium  hydroxide ; 
the  various  volumetric  methods  could  not  be  recom- 
mended because  of  the  unfitness  of  liquid  absorbents. 

"  For  this  reason  I  have  used  as  absorbents  dry 
phosphorus  pentoxide  and  dry  soda-lime,  of  which 
the  former  absorbs  only  water,  the  latter  only  carbon 


362 


GAS  ANALYSIS 


PAKT  III 


dioxide  and  water.  As,  however,  I  fully  agree  with 
Professor  Spring  that  the  chemical  method  (titra- 
tion)  is  the  most  reliable  of  all  the  older  methods,  I 
have  taken  the  trouble  to  obtain  a  series  of  parallel 
analyses  by  my  method  and  by  Pettenkofer's  method 
in  its  latest  improved  form.  Herr  C.  Sonden,  Engi- 
neer and  Chemist  of  the  Hygienic  Bureau  in  Stock- 
holm, has  been  so  kind  as  to  make  simultaneously 
with  me,  upon  certain  days  in  November  and  Decem- 
ber, 1885,  determinations  of  the  carbon  dioxide  in 
the  air,  using  for  the  purpose  large  quantities  (10 
liters)  of  atmospheric  air.  The  samples  of  air  were 
taken  on  the  balcony  of  the  laboratory  of  the 
High  School,  which  is  quite  centrally  located  in 
Stockholm. 

"At  the  same  time  psychrometric  determinations 
of  the  atmospheric  moisture  were  made  with  the 
instruments  from  the  Central  Meteorological  Station. 


•PI  .                      Determinations  of       Determinations  of 

Water                     Carbon  Dioxide 

Month 

Day 

Time 

Psychro- 
meter 

Pettersson's 
Methods 

Pettenkofer's 
Method 
(Sonden) 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

November 

1 

11.22 

0.968 

0.059 

u 

8 

10.50 

0.86 

0.801 

0.055 

0.052 

« 

15 

2.25 

0.41 

0.461 

0.039 

... 

u 

22 

10.55 

... 

... 

0.043 

... 

a 

27 

11.44 

0^46 

0.479 

0.044 

... 

December 

5 

10.17 

0.67 

0.718 

0.041 

0.044 

u 

6 

10.16 

0.24 

0.219 

0.046 

0.043 

u 

8 

9.26 

0.22 

0.213 

0.051 

0.056 

u 

u 

u 

... 

... 

... 

0.059 

u 

u 

u 

... 

... 

... 

0.066 

a 

9 

9.90 

0.25 

0.150 

... 

... 

CHAP,  vii      ANALYSIS   OF  ATMOSPHERIC   AIR  363 

"  As  already  stated,  the  figures  given  by  the  psy- 
chrometer  generally  agree  quite  well  with  the  analyti- 
cal results ;  a  noticeable  difference  was  seen  only  on 
the  9th  of  December,  when  the  temperature  of  the 
air  was  rather  low  (below -8°  C.).  A  greater 
agreement  between  the  determinations  of  carbon 
dioxide  by  such  different  methods  could  hardly  be 
expected. 

"  From  among  the  many  analyses  of  the  air  of  the 
laboratory,  which  in  themselves  are  of  but  little 
interest,  I  will  give  some  results  obtained  during 
the  preceding  week :  — 

May  6.  Moisture =0.640  per  cent  Carbon  dioxide  = 
"    7.           «        =0.687       «  "  =0.1 34  per  cent. 

"    8.          "       =0.877       "  "  =0.113       " 

44    9.  4'       =0.815      "  "  =0.109       " 

14  10.  «*        =0.754      "  '4 

"  I  am  endeavouring  at  the  present  time  to  apply 
the  same  analytical  principle  to  the  determination  of 
oxygen  in  the  atmosphere,  and  I  hope  later  to  be 
able  to  publish  something  on  that  subject." 

For  the  determination  of  carbon  dioxide,  Otto 
Fetter sson  and  A.  Palmqvist  have  materially  simpli- 
fied the  apparatus  just  described.  They  describe 
the  new  apparatus  as  follows  :  — 

"  Under  the  heading,  4  The  analysis  of  air  upon  a 
new  principle,'  published  in  the  Zeitschrift  fur  ana- 
lytische  Chemie,  25,  pp.  467  to  478,  one  of  us  has 
described  an  apparatus  for  volumetrically  determin- 
ing the  amounts  of  moisture  and  carbon  dioxide  in 
the  air  directly,  without  corrections  for  variations  of 


364  GAS  ANALYSIS  PART  in 

temperature  and  pressure.  Since  we  desired  to  make 
use  of  this  principle  for  the  sanitary  determination 
of  carbon  dioxide,  which  is  made  almost  exclusively 
by  the  exact  but  rather  complex  and  long  method  of 
Pettenkofer,  we  have  endeavoured,  with  the  coopera- 
tion of  C.  Sonden,  to  give  to  the  apparatus  described 
by  Pettersson  a  simpler  and  more  convenient  form, 
and  if  possible  to  reduce  the  length  of  each  deter- 
mination from  a  half  hour  or  more,  down  to  a  few 
minutes.  This  was  accomplished  by  analysing  the 
air  not  in  an  absolutely  dry  condition,  but  saturated 
with  moisture.  The  complete  drying  of  the  air  can 
be  done  only  with  phosphorus  pentoxide,  and  this 
takes  considerable  time.  When  dry  absorbents  are 
used  the  absorption  must  take  place  under  consid- 
erably increased  pressure,  a  circumstance  which  calls 
for  great  care  in  the  making  of  the  apparatus,  the 
construction  of  the  glass  stopcocks,  the  introduction 
of  the  absorbents,  etc.  In  using  moist  air  we  must 
give  up,  it  is  true,  the  direct  determination  of  the 
water  vapour,  but,  on  the  other  hand,  it  becomes 
possible  to  make  a  direct  determination  of  the  carbon 
dioxide  by  means  of  a  liquid  reagent,  and  the  analy- 
sis is  completed  in  a  few  minutes  without  the  tubes 
being  exposed  to  any  appreciable  increase  of  pressure. 
"  Figure  106  shows  the  apparatus  which  we  used, 
and  which  is  easily  portable.  The  apparatus  can  be 
covered  by  a  wooden  box  which  fits  over  it,  and  to 
which  a  metal  handle  is  strongly  fastened  (this  cover 
is  not  shown  in  the  figure).  When  the  apparatus 
has  been  brought  to  the  place  where  the  air  is  to  be 
examined,  the  glass  jacket  is  filled  with  water,  the 
outside  air  is  drawn  in  through  the  tube  c,  and  by 


FIG.  106. 


866  GAS   ANALYSIS  PART  in 

a  few  simple  manipulations,  which  take  only  a  few 
minutes,  the  carbon  dioxide  is  determined  with  an 
accuracy  of  about  0.01  per  cent.  The  dimensions 
of  the  apparatus  are  as  small  as  possible.  For  exam- 
ple, the  pipette  A  into  which  the  air  to  be  analysed  is 
drawn  holds  only  about  18  ccm.  With  larger  volumes 
of  air  it  would  be  easy  to  attain  greater  accuracy. 

"The  carbon  dioxide  is  absorbed  in  the  Orsat 
potash-tube  B,  and  the  air  is  measured,  before  and 
after  the  absorption,  in  the  pipette  A  and  its  gradu- 
ated tube.  The  measuring  pipette  can  be  filled  with 
mercury  or  air,  or  emptied  of  the  same,  by  raising 
or  lowering  the  mercury  reservoir  E,  which  is  joined 
to  the  lower  end  of  the  graduated  tube  of  A  by 
means  of  a  rubber  tube  wrapped  with  copper  wire. 
There  must  always  be  a  drop  of  water  on  the  surface 
of  the  mercury;  the  air  standing  over  the  mercury 
is  thus  kept  saturated  with  moisture.  In  reading 
the  volumes,  the  meniscus  of  the  mercury  is  each 
time  so  adjusted  that  the  pressure  in  A  is  exactly  - 
the  same  as  the  pressure  of  the  air  in  the  compensa- 
tion cylinder  Q. 

"  A  differential  manometer  containing  a  drop  of  a 
coloured  liquid  (petroleum,  in  which  azo-benzol  is 
dissolved),  and  connected  by  capillary  glass  tubes 
on  the  one  side  with  A  and  on  the  other  with  (7, 
serves  as  the  indicator  in  these  operations.  By  mov- 
ing the  reservoir  E  and  then  —  having  closed  the 
stopcock  d  —  suitably  turning  the  screw  e,  the  level 
of  the  mercury  in  A  is  so  adjusted  that  the  drop  of 
liquid  in  the  manometer  stands  at  zero.  It  is  obvi- 
ous that  in  this  manner  it  is  always  possible  to  bring 
back  the  air  in  A  to  the  same  pressure  as  that  pre- 


CHAP,  vii       ANALYSIS  OF  ATMOSPHERIC   AIR  367 

vailing  in  the  compensator  C.  Since  the  air  in  both 
the  compensator  and  pipette  is,  from  the  beginning 
of  the  experiment,  separated  from  the  external  at- 
mosphere by  closing  the  stopcocks  /,  #,  and  <?,  any 
variations  in  the  external  atmosphere  have  no  effect. 
This  is  also  true  of  changes  in  temperature ;  these 
eliminate  themselves  by  acting  in  the  same  manner 
and  to  the  same  extent  upon  the  tension  of  the  air 
in  A  and  (7,  provided  that  the  water  in  the  outer 
vessel  which  surrounds  the  main  parts  of  the  appa- 
ratus is  sufficiently  stirred.  For  these  reasons  no 
observation  of  temperature  or  barometric  pressure 
is  necessary.  The  changes  in  volume  read  off  on 
the  scale  give  directly  the  amount  of  carbon  dioxide 
in  hundredths  of  per  cent  by  volume. 

"  Since  the  air  is  saturated  with  moisture  before 
the  absorption,  it  is  clear  that  for  strict  correctness 
a  slight  correction  is  necessary  to  reduce  the  per 
cent  of  carbon  dioxide  found  in  the  air  saturated 
with  moisture  to  the  proper  figure  for  the  air  in  its 
actual  condition.  This  simple  correction  is,  how- 
ever, of  no  importance  because  it  is  so  small.  An 
example  will  make  this  clear.  Let  us  suppose  that 
the  temperature  is  23°  C.,  and  that  the  air  is  so  dry 
that  it  contains  only  0.66  per  cent  of  water  vapour 
at  a  barometric  pressure  of  760  mm.  The  actual 
amount  of  carbon  dioxide  present  is  then  ascertained 
by  means  of  the  equation :  — 

xi  (100  -0.66)  =0.04:  100 
z=  0.039736. 

The  result  of  the  analysis  is,  therefore,  0.000264  too 
high. 


368  GAS  ANALYSIS  PART  in 

"  Each  analysis  consists  of  three  operations. 

"  1.  The  air  is  drawn  in  from  the  outside  and  is 
measured,  the  level  of  the  mercury  in  the  graduated 
tube  being  brought  to  the  zero  mark.  The  upper 
and  narrower  part  of  the  scale,  where  each  division 
denotes  y^^o"  °f  ^e  v°lume  of  the  pipette,  is  used 
in  analyses  of  atmospheric  air,  or  the  ordinary  air  of 
rooms,  where  the  per  cent  of  carbon  dioxide  is  at  the 
most  not  higher  than  0.4  per  cent.  In  the  analysis 
of  very  impure  air  the  lower  part  of  the  graduated 
tube  is  used,  each  division  here  corresponding  to 
TfrW  °f  the  whole  volume.  In  measuring  the  vol- 
ume the  stopcocks/,  #,  6,  <?,  and  d  must  be  closed. 

"  2.  The  stopcocks  d  and  b  are  opened,  a  is  closed, 
and  the  air  is  passed  from  A  to  B.  After  one  or 
two  minutes  the  carbon  dioxide  is  absorbed  and  the 
air  may  be  brought  back  into  J.,  b  is  then  closed,  and 
a  is  opened. 

"  3.  The  mercury  level  in  A  is  so  adjusted  that 
the  index  again  takes  its  normal  position.  The  de- 
crease in.  volume  is  then  read  off  on  the  scale. 

"  The  following  table  contains  some  parallel  deter- 
minations which  were  simultaneously  made  with  the 
same  samples  of  air :  (1)  with  the  apparatus  just 
described;  (2)  with  a  larger  apparatus  constructed 
upon  the  same  principle  by  Sonden ;  and  (3)  by  Pet- 
tenkofer's  method.  It  is  worthy  of  mention  that  in 
such  parallel  analyses,  if  they  are  to  give  results 
really  exact  to  0.01  per  cent,  the  air  must  not  be 
taken  directly  from  the  room,  because  the  air  of  a 
room  is  not  always  homogeneous.  The  air  samples 
must  be  taken  from  volumes  of  air  confined  in 
special  reservoirs. 


CHAP,  vii       ANALYSIS   OF  ATMOSPHERIC   AIR 


Determination 

Determination 

Determination 

Series  of 
Experiments 

of  Carbon 
Dioxide  with 
the  Portable 

of  Carbon 
Dioxide  with 
Sonden's 

of  Carbon 
Dioxide  by 
Pettenkofer's 

Apparatus 

Apparatus 

Method 

I. 

a 

0.030  per  cent 

0.041  per  cent 

... 

b 

0.030 

0.038       " 

... 

II. 

a 

0.460 

0.463       " 

... 

b 

0.450 

... 

... 

III. 

a 

0.195 

0.211       « 

0.22  per  cent 

b 

0.205 

0.206       " 

0.21       « 

c 

0.210 

0.210       " 

... 

IV. 

a 

0.230 

0.227       " 

0.23    "'« 

b 

0.225 

0.223       " 

0.23       " 

c 

0.220 

... 

V. 

a 

0.080 

0.077  "'  " 

0.10   "'« 

b 

0.070 

... 

0.09       " 

VI. 

a 

0.170 

0.170       " 

... 

"Any  impurities  in  the  measuring  tube  may  be 
easily  removed  by  rinsing  the  pipette  with  water 
which  is  drawn  in  and  driven  out  through  c. 

"  We  would  in  passing  call  attention  to  the  fact 
that  the  Pettenkof  er  method  can  be  very  much  short- 
ened by  closing  the  bottle  in  which  the  water  is  to 
be  shaken  with  the  barium  hydroxide  solution,  not 
with  a  cap  but  with  a  tightly  fitting  perforated  rub- 
ber stopper,  through  which  is  inserted  a  glass  tube 
reaching  to  the  bottom  of  the  bottle.  This  glass 
tube  has,  at  two  or  three  different  places,  loosely  in- 
serted stoppers  of  pure  cotton. 

"  After  shaking  the  bottle,  the  glass  tube  can  be 
connected  with  the  branch  tube  of  a  glass  stopcock 
burette,  and  the  excess  of  barium  hydroxide  can  be 
drawn  up  into  the  burette  and  immediately  titrated. 

"  The  baryta  water  may  be  somewhat  cloudy  after 
passing  the  first  stopper  of  cotton,  but  it  is  filtered 
SB 


370  GAS  ANALYSIS  PART  in 

by  the  second  and  third,  and  enters  the  burette  per- 
fectly clear. 

"  Sulphur  dioxide  can  also  be  titrated  in  the  same 
way." 


3.    Carbon  Monoxide 

On  account  of  the  very  poisonous  nature  of  car- 
bon monoxide  it  is  important  in  sanitary  examina- 
tions of  the  air  to  determine  the  absence  or  presence 
of  this  gas.  The  blood  reaction,  which  is  fully  de- 
scribed on  p.  211,  is  best  adapted  to  this  purpose. 


4.    The  Determination  of  Oxygen  in  the  Atmosphere 

The  great  significance  which  the  oxygen  in  the 
atmosphere  has  for  all  living  beings  has  made  the 
determination  of  this  gas  the  subject  of  frequent 
investigations. 

Of  the  many  methods  which  have  been  used  for 
this  purpose,  that  one  which  was  original  with  Jolly 
and  was  elaborated  by  Kreusler  is  one  of  the  most 
exact.  In  1886  and  1887  the  author,  in  cooperation 
with  Kreusler  and  Morley,  made  a  number  of  analy- 
ses of  atmospheric  air.  In  these  investigations 
Kreusler  determined  the  oxygen  by  causing  it  to 
unite  with  glowing  copper,  Morley  by  combustion 
with  hydrogen,  and  the  author  by  absorbing  the 
oxygen  with  alkaline  pyrogallol.  By  paying  great 
care  to  all  the  necessary  precautions,  closely  agreeing 
results  were  obtained  by  the  three  different  methods. 

The  description  of  the  method  used  by  the  author 
is  given  below. 


CHAP,  vii       ANALYSIS   OF  ATMOSPHERIC   AIR  371 

THE  DETERMINATION  OF  OXYGEN  WITH  THE 
HEMPEL  APPARATUS  FOR  EXACT  GAS 

ANALYSIS1    (p.  79) 

The  arrangement  of  the  apparatus  has  already 
been  described  in  detail,  so  that  only  a  few  particu- 
lars that  are  of  importance  in  very  accurate  work 
will  here  be  given. 

The  samples  of  air  were  collected  in  glass  tubes 
which  had  been  previously  exhausted  of  air,  as  de- 
scribed on  p.  6.  The  glass  tubes  were  opened  in  a 
small  mercury  trough  by  breaking  off  the  end  of  the 
tube  with  ordinary  pliers.  A  small  crucible  was 
then  slipped  under  the  tube,  and  the  tube  was  thus 
lifted  out  and  put  in  a  cylinder.  The  air  was  then 
drawn  over  into  a  gas  pipette  containing  a  very 
little  water.  This  pipette  was  kept  where  it  was 
somewhat  warmer  than  the  room  in  which  the  analy- 
sis was  to  be  made.  On  days  when  the  gas  labora- 
tory had  to  be  heated,  the  pipette  stood  near  the 
heating  tube.  In  this  simple  manner  the  gas  to  be 
analysed  was  saturated  with  water,  so  that  later  it 
was  not  necessary  to  moisten  the  measuring  bulb. 
The  measuring  bulb  was  cleaned  before  each  deter- 
mination, and  after  being  dried  it  was  brought  into 
the  mercury-trough  of  the  apparatus  by  placing  it  in 
two  porcelain  crucibles,  one  within  the  other  (see 
Fig.  107),  and  filling  these  with  mercury.  If  these 
are  then  lowered  through  the  cooling  water  of  the 
trough  into  the  mercury,  and  the  longer  crucible 
removed  by  lowering  it  still  further,  the  measuring 

1  Berichte  der  deutschen  chemischen  Gesellschaft,  1885,  267  j 
1887,  1864. 


372 


GAS  ANALYSIS 


PART  III 


bulb  may  now  be  lifted  out  of  the  small  crucible 
under  the  surface  of  the  mercury  without  a  trace  of 
water  entering  it.  If  only  one  crucible  is  used, 
water  may  easily  get  into  the  bulb,  the  probable 
cause  being  surface  adhesion.  With  the  instrument 
shown  in  Fig.  108  the  air  was  then  sucked  out  of 
the  measuring  bulb  and  the  gas  sample  was  passed 
in  from  the  gas  pipette,  great  care  being  taken  that 
no  trace  of  water  entered  the  bulb. 


FIG.  107. 


FIG.  108. 


The  readings  of  the  pressure  on  the  scale  of  the 
barometer  tube  were  repeated  every  three  minutes 
until  there  was  no  difference  between  two  readings. 

The  pipette  was  filled  with  alkaline  pyrogallol 
with  the  apparatus  described  on  p.  153.  After  fill- 
ing, the  capillary  of  the  pipette  was  placed  in  a 
beaker  of  water,  and  the  capillary  was  freed  from 
the  reagent  by  carefully  drawing  in  and  driving  out 
a  little  water. 

When  this  washing  was  completed,  as  may  be  told 
with  ease  from  the  formation  of  the  streaks  in  the 


CHAP,  vii      ANALYSIS  OF   ATMOSPHERIC   AIR  373 

water,  the  capillary  of  the  pipette  was  placed  in  a 
beaker  of  fresh  distilled  water  and  a  water-thread 
about  3  mm.  long  was  drawn  in.  The  capillary  was 
then  carefully  dried  on  the  outside.  The  gas  was 
next  drawn  over  into  the  pipette  thus  made  ready, 
and  the  absorption  of  the  oxygen  was  effected  by 
shaking  the  pipette  for  five  minutes.  The  advan- 
tage of  the  short  thread  of  water  in  the  capillary  is 
that  when  the  gas  is  drawn  into  the  pipette  the 
water  once  more  rinses  the  capillary  throughout  its 
entire  length. 

After  the  absorption  another  short  thread  of  water 
was  drawn  into  the  capillary  by  immersing  the  latter 
in  distilled  water,  the  pipette  was  then  brought  into 
position  in  the  apparatus,  and  before  driving  the  gas 
back  into  the  measuring  bulb  mercury  was  sucked 
into  the  pipette  through  the  capillary,  the  mercury 
driving  the  little  thread  of  water  before  it.  Upon 
blowing  into  the  pipette  the  gas  now  passes  into  the 
measuring  bulb,  being  saturated  with  water  vapour  in 
its  passage  through  the  freshly  moistened  capillar}^. 

It  is  thus  easy  to  prevent  any  trace  of  the  reagent 
from  entering  the  measuring  bulb.  The  agreement 
of  the  results  is  quite  remarkable.  The  pipette 
must  be  frequently  cleaned  by  drawing  water  into 
it  so  that  muddy  particles  will  not  adhere  to  the 
glass. 

An  idea  of  the  accuracy  which  can  be  attained 
by  this  method  may  be  formed  from  the  following 
figures. 

In  analyses  of  air  samples  kept  in  fused  glass 
tubes  my  assistants,  working  more  than  a  year  apart, 
found  — 


374  GAS  ANALYSIS  PART  in 

0       ,  Schumann 

(One  year  later) 

Air  of  April  14,  1886    .     .     .     20.89  per  cent     20.89  per  cent 
Air  of  April  5,  1886      .     .     .     20.93         "  20.94         " 

In  four  analyses  of  the  same  sample  Oettel  found — 

20.936  per  cent  20.938  per  cent 

20.938        «  20.938        " 

To  permit  of  a  comparison  between  the  combus- 
tion method  with  copper  and  the  absorption  method 
with  alkaline  pyrogallol,  Herr  Kreusler  had  the 
kindness  to  collect  samples  on  three  different  days 
and  to  send  them  to  Dresden.  These  samples  were 
first  analysed  by  my  method  by  Herr  Oettel  in  Dres- 
den, and  later  by  Herr  Tacke  and  Herr  Kreusler  in 
Bonn.  The  results  are  given  on  p.  150. 

5.  Ozone 

For  the  detection  and  determination  of  ozone,  see 
p.  161. 

6.  Argon 

For  details  concerning  Argon,  see  p.  168. 

7.   Sulphur  Dioxide  and  Sulphuric  Acid 

To  detect  very  small  amounts  of  sulphur  dioxide 
and  sulphuric  acid  in  the  atmosphere  Ost  recom- 
mends that  pieces  of  linen  cloth  be  dipped  into 
strong  baryta  water,  then  treated  with  carbon  di- 
oxide, and  that  these  strips  be  hung  up  in  the  air 
for  several  weeks  or  months.  The  presence  of  sul- 
phuric acid  in  the  cloth  is  then  detected  by  burning 


CHAP,  vii      ANALYSIS   OF  ATMOSPHERIC   AIR  375 

the  cloth  and  testing  the  ash.  H.  Wislicenus  found 
that  it  was  necessary  to  first  treat  the  cloth  with 
hydrochloric  acid  and  water  to  free  it  from  all  sul- 
phur compounds  which  it  might  contain.  The  detec- 
tion and  determination  of  the  sulphuric  acid  is  carried 
on  by  first  incinerating  the  cloth  and  then  fusing  a 
part  of  the  ash  with  sodium  carbonate  to  transform 
the  barium  sulphate  into  sodium  sulphate  and  barium 
carbonate.  The  sodium  sulphate  is  then  extracted 
with  water,  and  the  sulphuric  acid  is  determined 
in  the  usual  manner  by  precipitation  as  barium 
sulphate. 

8.    Nitrogen 

Up  to  the  present  time  no  convenient  and  accurate 
method  for  determining  free  nitrogen  is  known. 


CHAPTER   VIII 


EXAMINATION   OF  THE   GASES  WHICH  ARE 
PRODUCED  BY  LIVING  BACTERIA 

W.  HESSE  has  carried  on  in  the  author's  laboratory 
a  long  series  of  investigations  upon  the  gases  evolved 
from  growing  bacteria. 

From  the  very  nature  of  the  case  it  is  apparent 
that  in  such  an  examination  we  must  endeavour  to 
work  with  as  small  quantities  of  substance  as  is 
possible. 

Hesse  used  the  •  apparatus  shown  in  Fig.  109  for 
the  bacteria  cultures.  This  consists  of  a  small 
Erlenmeyer  flask  of  about  50  ccm.  contents,  in  the 

neck  of  which  is  inserted  a 
glass  stopper  carrying  two 
glass  tubes  after  the  manner 
of  a  Drechsel  wash-bottle. 
Each  tube  is  provided  with 
a  carefully  ground  glass  stop- 
cock, a  tube  beyond  each 
stopcock  being  capillary.  If 
it  is  desired  to  avoid  any 
possibility  of  the  passage  of 
gas  through  the  lubricant 
of  the  stopcocks,  these  may 

be  given  the   form  shown  in  Fig.   74  c  and  d  on 
p.  171,   which   permits    of    their   being    covered   by 

376 


FIG.  109. 


CHAP,  vin     GASES   PRODUCED   BY  BACTERIA  377 

mercury.  The  stopper  of  the  flask  is  also  covered 
with  mercury  in  the  manner  shown  in  Fig.  109. 

A  suitable  culture  medium  b  is  placed  in  the  flask 
and  this  is  then  inoculated  with  the  bacteria  which 
are  to  be  examined.  The  apparatus  renders  it 
possible  to  carry  on  the  culture  in  air  or  in  any 
other  desired  gas,  the  gas  being  led  into  the  flask 
through  the  stopcocks.  To  examine  the  gas  which 
may  be  set  free  during  the  growth  of  the  bacteria, 
the  apparatus  is  connected  by  means  of  a  three-way 
capillary  (Fig.  40)  with  a  gas  burette  of  the  con- 
struction shown  in  Fig.  36,  III.  The  widening  of 
the  lower  portion  of  the  measuring  tube  of  the 
burette  renders  it  possible  to  employ  the  burette  as 
an  aspirator  and  to  easily  draw  out  from  the  flask 
10  ccm.  of  the  gas  which  it  contains. 

This  gas  is  measured  in  the  burette  and  is  then 
brought  into  contact  with  the  proper  absorbents  in 
small  pipettes,  every  trace  of  air  being  excluded 
throughout  the  analysis  by  the  use  of  the  three-way 
capillary  shown  in  Fig.  40.  All  operations  are  per- 
formed over  mercury,  and  the  pipettes  are  filled 
with  mercury  and  the  reagents.  The  bulbs  of  the 
pipettes  need  not  have  a  greater  capacity  than 
20  cc.,  and  they  may  have  the  form  shown  in 
Figs.  31  and  32  or  Figs.  37  and  38. 


CHAPTER   IX 

THE  DETERMINATION  OF  FLUORINE   AS   SILICON 
TETRAFLUORIDE 

AT  the  suggestion  of  the  author,  O.  W.  F.  Oettel 
has  worked  out  a  method  for  the  determination  of 
the  fluorine  in  a  substance,  the  fluorine  being  evolved 
as  silicon  tetrafluoride,  and  the  volume  of  this  gas 
then  being  directly  measured.  Since  a  large  number 
of  substances  contain  both  fluorine  and  carbon  di- 
oxide, the  author  and  W.  Scheffler1  have  devised 
a  method  which  permits  of  the  simultaneous  deter- 
mination of  fluorine  and  carbon  dioxide  in  a  single 
sample.  The  fluorine  is  set  free  as  silicon  tetra- 
fluoride together  with  carbon  dioxide  in  a  suitable 
apparatus,  is  collected  in  a  burette,  and  the  silicon 
tetrafluoride  is  then  decomposed  and  absorbed  by 
means  of  water  (a  small  volume  of  carbon  dioxide 
is  here  taken  up  by  the  water).  The  carbon  dioxide 
still  present  in  the  gas  is  then  completely  removed 
by  passing  the  gas  into  a  pipette  containing  caustic 
potash.  The  gas  residue  is  again  brought  over  the 
water  which  was  first  used  and  by  which  the  silicon 
tetrafluoride  was  absorbed;  the  absorbed  carbon 
dioxide  hereupon  escapes  from  the  water  and  passes 
into  the  gas  residue.  Upon  transferring  the  gas 

1  Walther  Hempel  and  W.  Scheffler,  Zeitschr.  f.  Anorgan. 
Chemie,  1897,  20,  1. 

378 


CHAP,  ix         DETERMINATION   OF   FLUORINE  379 

once  more  to  the  caustic  potash  pipette,  the  re- 
mainder of  the  carbon  dioxide  is  removed,  and  this 
volume  is  subtracted  from  the  diminution  first  ob- 
tained by  the  absorption  with  water.  The  difference 
gives  the  amount  of  silicon  tetrafluoride. 

In  this  manner  it  is  possible  to  make  very  sharp 
determinations  of  fluorine  in  the  presence  of  carbon 
dioxide. 

For  setting  free  the  silicon  tetrafluoride  there  is 
used  the  apparatus  shown  in  Fig.  110,  II,  which 
has  already  been  described  on  p.  75,  Fig.  42.  The 
evolution  flask  is  connected  with  a  simple  gas 
burette  filled  with  mercury  and  containing  on  top 
of  the  mercury  some  concentrated  sulphuric  acid. 
It  is  well  to  join  to  the  burette  a  level-bulb  instead 
of  a  level-tube,  and  to  attach  a  glass  stopcock  to  the 
lower  end  of  the  burette  tube  (see  Fig.  110). 

The  substance  under  examination  is  mixed  with 
finely  powdered  quartz,  the  weight  of  the  quartz 
being  fifteen  times  that  of  the  fluorine  which  is  prob- 
ably present  in  the  material.  The  quartz  is  first 
heated  for  a  long  time  in  a  muffel  furnace  under 
free  access  of  air  to  remove  every  trace  of  organic 
matter. 

The  sulphuric  acid  to  be  employed  must  be  freed 
from  organic  substances  and  from  oxides  of  nitrogen. 
This  is  accomplished  by  adding  to  the  concentrated 
sulphuric  acid  about  5  g.  of  powdered  sulphur  and 
then  fuming  down  the  acid  to  two-thirds  of  its  origi- 
nal volume. 

In  carrying  out  a  determination  the  evolution  flask 
II  is  first  carefully  dried  and  the  substance,  together 
with  the  proper  amount  of  quartz  powder,  is  then 


380 


GAS  ANALYSIS 


PART  III 


introduced  into  the  flask  by  means  of  a  long  weigh- 
ing tube,  and  the  two  powders  are  mixed  as  inti- 
mately as  possible  by  shaking  the  flask.  The  flask 
is  then  joined  by  means  of  the  capillary  d  and  a 


FIG.  110. 


piece  of  dry  rubber  tubing  to  the  gas  burette  I  which 
contains  mercury  and  some  sulphuric  acid,  as  above 
described.  The  rubber  tube  is  held  firmly  in  place 
by  means  of  ligatures  of  light  iron  wire.  The  vol- 


CHAP,  ix          DETERMINATION  OF  FLUORINE  381 

ume  of  concentrated  sulphuric  acid  which  is  placed 
in  the  pipette  amounts  to  only  about  0.25  com.  Its 
presence  is  necessary  to  avoid  the  possibility  of  de- 
composition of  the  silicon  tetrafluoride  by  any  mois- 
ture that  might  be  in  the  burette. 

In  the  bells  I  and  m  is  placed  some  of  the  highly 
concentrated  sulphuric  acid.  A  water  suction  pump 
is  now  connected  to  k,  and  the  flask  II  is  par- 
tially exhausted.  The  stopcock  n  is  then  closed, 
and  upon  lifting  the  tube  o  sulphuric  acid  flows  down 
from  m  into  the  flask.  The  flask  is  shaken  so  as  to 
bring  the  acid  into  intimate  contact  with  the  mixture 
of  quartz  and  the  substance,  and  the  contents  of  the 
flask  is  then  heated  fully  up  to  the  boiling-point  of 
sulphuric  acid,  the  heating  being  continued  for  about 
fifteen  minutes. 

If  the  apparatus  should  break,  the  operator  might 
be  seriously  injured  by  the  hot  concentrated  sul- 
phuric acid.  It  is  well,  therefore,  to  protect  the 
eyes  with  goggles,  and  to  place  a  glass  screen  between 
the  flask  and  the  operator. 

The  heating  is  now  stopped,  and  the  gas  in  the 
flask  is  completely  driven  over  into  the  burette  by 
filling  m  with  some  of  the  concentrated  sulphuric 
acid  and  carefully  lifting  the  tube  o.  The  flask  is 
then  disconnected  from  the  burette  and  the  total 
volume  of  the  evolved  gases  is  measured. 

The  burette  is  now  connected  in  the  ordinary 
manner,  by  means  of  a  capillary  tube,  with  a  simple 
mercury  absorption  pipette  of  the  form  shown  in 
Fig.  Ill,  the  pipette  containing  5  ccm.  of  water 
above  the  mercury.  The  gas  is  transferred  to  the 
pipette  and  shaken  for  five  minutes  with  the  water. 


382 


GAS  ANALYSIS 


It  is  then  brought  back  into  the  burette  and  the 
diminution  in  volume  is  read  off. 

The  remaining  gas  is  passed  into  a  pipette  filled 
with  a  solution  of  potassium  hydroxide  to  absorb 

carbon  dioxide,  and 
is  then  drawn  back 
into  the  gas  burette. 
The  volume  is  ob- 
served, and  the  gas  is 
now  passed  into  the 
first  pipette,  Fig.  Ill, 
and  shaken  again  for 
three  minutes.  It  is 
then  passed  back  into 
the  burette,  and  the 
residual  volume  of 
gas  is  measured. 
This  gas  is  then 
passed  once  more 
into  the  potassium 
hydroxide  pipette  to 
determine  the  small 
FIG.  in.  amount  of  carbon 

dioxide     which     was 

taken  up  by  the  water  used  in  the  first  absorption 
of  the  silicon  tetrafluoride. 

All  of  these  operations  can  be  carried  out  with 
considerable  speed,  and  it  is  therefore  easily  possible 
to  make  a  determination  of  fluorine  in  two  hours. 

As  an  example  of  the  accuracy  of  the  method,  the 
following  result  may  be  cited:  2.156  g.  of  the  sub- 
stance gave  3.56  ccm.  of  silicon  tetrafluoride,  while 
theory  called  for  3.45  ccm. 


CHAP,  ix          DETERMINATION  OF   FLUORINE  383 

ANALYSIS  OF  TEETH 

It  was  found  upon  experiment  that  both  calcium 
fluoride  and  sodium  fluoride  lost  weight  when  heated 
to  about  1000°. 

1.495  g.  of  calcium  fluoride  lost  upon  ignition  at 
1000°  for  fifteen  minutes  0.019  g.,  at  red  heat 
0.0005. 

4.367  g.  of  sodium  fluoride  lost  at  1000°  0.104  g., 
at  red  heat  0.00075  g. 

Experiments  were  then  made  to  ascertain  whether 
it  is  possible  to  incinerate  teeth  without  loss  of 
fluorine.  With  this  object  in  view,  finely  pul- 
verised teeth  were  burned  in  a  combustion  fur- 
nace in  a  current  of  oxygen.  A  roll  of  fine-mesh 
platinum  wire-gauze  5  cm.  long  was  placed  before 
the  layer  of  the  substance,  and  behind  the  sub- 
stance there  was  a  10  cm.  layer  of  pieces  of 
marble  as  large  as  peas.  During  the  combustion, 
these  pieces  of  marble  were  heated  to  about  100°. 
The  purpose  of  their  introduction  is  to  retain  any 
calcium  fluoride  or  sodium  fluoride  which  might 
be  volatilised.  After  that  part  of  the  tube  in 
which  the  platinum  wire-gauze  is  placed  has  been 
heated  to  bright  redness,  the  substance  is  heated 
little  by  little  in  a  slow  current  of  oxygen,  and  all 
organic  substance  is  completely  burned.  The  marble 
showed  no  trace  of  fluorine  when  examined  after  the 
conclusion  of  the  experiment. 

The  incineration  of  teeth  is  easily  effected  in  a 
hard  glass  tube  in  a  current  of  oxygen  if  the  powder 
is  very  fine  and  is  placed  in  the  tube  in  a  very  thin 
layer. 


384  GAS   ANALYSIS  PART  in 

In  determining  fluorine  in  material  which  contains 
organic  matter,  it  is  very  important  that  the  sub- 
stance should  be  completely  incinerated,  since  the 
slightest  trace  of  residual  carbon  would  act  upon 
the  boiling  sulphuric  acid  and  cause  the  formation 
of  sulphur  dioxide,  a  gas  which  would  then  be  ab- 
sorbed by  water  when  the  silicon  tetrafluoride  is 
determined.  In  the  analysis  described  below,  the 
teeth  were  incinerated  in  the  manner  just  mentioned. 

HORSES'  TEETH 
Analysis  I 

2.332  g.  of  the  ash  of  the  teeth  was  decomposed 
in  the  apparatus  shown  in  Fig.  110.  The  evolved 
gas,  on  shaking  with  water,  gave  a  diminution  of 
2.05  ccm. ;  in  a  caustic  potash  pipette,  16.12  ccm. 
of  carbon  dioxide ;  on  shaking  the  gas  residue 
with  the  water  which  had  been  used  for  absorb- 
ing the  SiF4,  an  increase  in  volume  of  0.95  ccm., 
of  which  0.65  ccm.  was  absorbed  by  caustic  potash. 
The  volume  of  SiF4  is,  therefore,  2.05-0.65  = 
1.4  ccm.,  corresponding  to  0.2  per  cent  fluorine. 

Analysis  II 

2.274  g.  of  the  teeth  ash  gave  with  water  a  dimi- 
nution of  3.2  ccm. ;  and,  after  subtracting  the  carbon 
dioxide  absorbed  by  the  water,  2.6  ccm.  SiF4,  corre- 
sponding to  0.39  per  cent  fluorine.  The  carbon 
dioxide  originally  contained  in  the  gas  mixture 
amounted  to  15  ccm. 


CHAP,  ix          DETERMINATION   OF  FLUORINE  385 

Analysis  III 

2.419  g.  of  the  teeth  ash  gave,  after  subtracting 
the  carbon  dioxide,  2.2  ccm.  SiF4,  corresponding  to 
0.31  per  cent  fluorine.  The  carbon  dioxide  contained 
in  the  original  gas  mixture  amounted  to  15.9  ccm. 

HUMAN  TEETH 

Two  samples  of  unsound  teeth  and  four  samples 
of  sound  teeth  were  examined.  Two  teeth  were 
used  in  each  analysis,  and  were  incinerated  sepa- 
rately. The  results  follow  :  — 


Human 
Teeth 

Grams 
of 
Teeth 
Ash 
taken 

SiF4 

+ 
CO2 
found 

CO2 

whic'h 
was 
taken  up 
by  the 
water 

SiF4 
in 
cubic 
centi- 
meters 

Fluorine 
in 
Grams 

Per  cent 
of 
Fluorine 
in  the 
Teeth 
Ash 

Unsound 

1.793 

1.0 

4.65 

1.0 

0.0034 

0.19 

Sound 

1.434 

1.5 

5.80 

0.4 

1.4 

0.0047 

0.33 

Sound 

0.831 

1.6 

3.50 

1.6 

0.0054 

0.52 

2o 


CHAPTER   X 

APPARATUS  FOR  THE  ANALYSIS  OF  SALTPETER 
AND  THE  NITRIC  ACID  ESTERS  (NITRO-GLYC- 
ERIN,  GUN-COTTON,  ETC.) 

WALTER  CBUM  1  has  found  that  the  nitrogen  acids 
dissolved  in  sulphuric  acid  (nitrogen  trioxide,  nitro- 
gen peroxide,  and  nitric  acid)  are  completely  reduced 
to  nitric  oxide  by  shaking  with  mercury  at  ordinary 
temperatures.  John  Watts  2  and  Georg  Lunge  3  have 
worked  out  this  method  still  further,  and  the  latter 
has  constructed  an  apparatus  therefor  which  he  calls 
a  nitrometer.  The  author  first4  used  the  reaction 
for  the  decomposition  of  the  nitric  acid  esters,  and  in 
particular  for  the  determination  of  the  nitro-glycerin 
in  dynamite.  Lunge  has  determined  the  conditions 
under  which  it  is  possible  to  analyse  saltpeter  in  the 
same  manner. 

The  above-mentioned  analyses  may  be  easily  carried 
out  in  the  apparatus  here  described  (Fig.  112). 

The  apparatus  consists  of  the  evolution  cylinder  <?, 
the  level-bulb  e,  and  the  gas  burette  ab.  c  has  at  the 
top  a  glass  stopcock  t,  and  near  the  bottom  a  side  tube 
x.  It  is  closed  by  a  double-bore  rubber  stopper,  over 
whioh  passes  a  metallic  band  to  keep  it  from  being 

1  Ann.  d.  Chem.  u,  Pharm.,  62,  233 ;   also  Jour.  f.  prakt.  Chemie 
41,  201. 

2  Chemical  News,  37,  45. 

3  Berichte  der  deutschen  chemischen  Gesellschaft,  11,  434. 
*  Zeitechrift  fur  analyt.  Chemie,  20,  82. 


Fio.  112. 


388  GAS   ANALYSIS  PART  in 

forced  out  by  the  pressure  of  the  mercury.  The 
long  handle  of  the  weighing-tube  k  passes  through 
one  opening  of  the  stopper,  and  through  the  other  is 
inserted  the  bent  tube  Z,  which  is  joined  to  the  level- 
bulb  e  by  the  rubber  tube  m.  The  bulb  e  is  supplied 
with  a  glass  stopcock  o. 

To  use  this  apparatus  for  the  evaluation  of  dyna- 
mite or  other  nitric  acid  ester,  fill  the  bulb  e  com- 
pletely with  mercury,  o  being  closed  ;  insert  &, 
containing  the  weighed  substance,  in  the  rubber 
stopper,  and  put  the  apparatus  together  as  shown 
in  Fig.  112.  The  gas  burette,  however,  is  not  yet 
connected  with  i.  By  opening  o  and  i  and  raising  e, 
c  is  completely  filled  with  mercury.  The  stopcock  i 
is  then  closed.  If  now  the  sulphuric  acid  required 
for  the  decomposition  be  poured  into  x,  the  acid  may 
easily  be  brought  into  c  by  lowering  the  bulb  e.  The 
entrance  of  the  sulphuric  acid  can  be  stopped  at  any 
moment  by  closing  the  stopcock  0,  and  the  introduc- 
tion of  air  may  be  very  easily  avoided. 

Atmospheric  pressure  is  then  reestablished  in  the 
apparatus  by  raising  e  and  opening  0,  and  c  is  shaken 
until,  with  stopcock  o  closed,  no  rise  of  mercury  can 
be  observed  in  x  after  renewed  shaking. 

When,  with  o  closed,  the  mercury  in  x  remains  at 
the  same  height  after  two  shakings  of  0,  the  reaction 
is  ended.  The  cup  k  should  be  just  deep  enough  to 
easily  hold  the  substance  ;  it  is  desirable  to  have  cups 
of  different  sizes  to  correspond  to  the  volume  of  the 
material  to  be  analysed. 

When  the  evolution  of  gas  is  complete,  c  is  con- 
nected with  the  gas  burette,  which  is  filled  with 
mercury,  and  which  has  been  previously  moistened 


CHAP,  x  ANALYSIS   OF   SALTPETER  389 

with  a  very  little  water.  The  nitric  oxide  is  then 
drawn  into  the  burette  by  opening  0,  t,  and  6?,  and 
raising  the  bulb  e.  The  gas  is  then  measured  in  the 
usual  manner,  with  allowance  for  the  tension  of  the 
water  vapour,  and  the  calculation  is  made. 

To  clean  the  apparatus,  drive  as  much  of  the  mer- 
cury as  possible  back  into  the  bulb  e,  close  0,  and 
open  the  cylinder  c  over  a  large  beaker  of  water  so 
as  to  catch  the  mercury,  and  at  the  same  time  sepa- 
rate it  from  the  sulphuric  acid,  c  is  rinsed  out  with 
water,  and  after  drying  the  weighing  tube  k,  the 
apparatus  is  ready  for  a  new  determination.  If  the 
warming  of  the  gas  burette  with  the  hands  has  been 
avoided,  the  measurement  can  be  made  in  a  very  few 
minutes.  The  readings  are,  of  course,  very  sharp, 
because  there  is  no  sulphuric  acid  in  the  gas  burette. 

To  test  the  purity  of  the  nitric  oxide  obtained, 
the  gas  is  led  into  a  double  gas  pipette  containing  a 
solution  of  a  ferrous  salt ;  the  evolved  carbon  dioxide 
may  be  absorbed  in  a  pipette  containing  potassium 
hydroxide  solution. 

The  analytical  absorbing  power  of  a  saturated  solu- 
tion of  ferrous  chloride  is  14,  of  ferrous  sulphate  3 
to  4i. 

To  analyse  saltpeter  in  the  above  apparatus,  the 
substance  must  first  be  dissolved  in  a  very  little 
water. 

E.  B.  Hagen  has  used  the  apparatus  very  often  for 
the  analysis  of  gun-cotton,  and  has  devised  for  this 
purpose  a  manipulation  which  admits  of  very  accurate 
and  easy  work. 

Hagen  purposely  moistens  the  vessel  c,  if  it  is  not 
already  sufficiently  moist  from  the  preceding  analysis, 


890  GAS  ANALYSIS  PART  m 

and  then  introduces  into  the  inverted  apparatus  a 
weighed  amount  of  gun-cotton,  which  has  previously 
been  finely  divided  with  a  knife  or  rasp.  The  ap- 
paratus is  then  put  together,  the  gun-cotton  ad- 
hering to  the  walls  of  the  vessel  because  of  the 
moisture  present.  c  is  then  placed  in  a  slanting 
position,  as  shown  in  Fig.  113,  and  mercury  is  run  in 
until  only  a  few  cubic  centimeters  of  air  remain  in 
the  cylinder.  The  stopcock  o  is  now  closed  and  c  is 
shaken.  This  thoroughly  moistens  the  powder  with 
water.  The  air  is  now  completely  driven  out  of  c  by 
allowing  the  mercury  to  enter. 

After  the  introduction  of  the  concentrated  sul- 
phuric acid  c  is  shaken  for  three  minutes,  and  when 
the  gun-cotton  is  dissolved  in  the  acid  c  is  heated 
directly  with  the  Bunsen  burner  (Fig.  113),  and  is 
shaken  as  long  as  evolution  of  gas  results.  The 
nitric  oxide  which  is  set  free  is  now  measured  in  the 
manner  previously  described.  Many  samples  of  gun- 
cotton  contain  some  calcium  carbonate,  and  hence 
the  possibility  of  the  presence  of  some  carbon  dioxide 
should  be  not  overlooked. 

Especial  attention  should  be  called  to  the  fact  that 
too  much  sulphuric  acid  must  not  be  used :  15  ccm. 
suffices  in  all  cases.  On  account  of  the  solubility  of 
nitric  oxide  in  sulphuric  acid,  a  correction  depending 
upon  the  amount  of  acid  used  must  be  brought  into 
the  calculation.  For  15  ccm.  of  sulphuric  acid  0.21 
ccm.  is  to  be  considered  as  having  gone  into  solution. 
The  advantage  of  the  apparatus  lies  in  the  great  speed 
with  which  the  work  may  be  done.  If  the  burette 
stand  where  the  temperature  is  uniform,  and  if  the 
apparatus  be  brought  near  the  burette  only  for  the 


ANALYSIS   OF   SALTPETER 


391 


purpose  of  transferring  the  gas,  then  two  analyses  may 
easily  be  made  in  an  hour,  since  under  these  circum- 


Fm.  113. 


stances  the  readings  of  the  gas  volumes  may  be  made 
after  ten  minutes  at  the  longest. 


CHAPTER  XI 

THE  DETERMINATION  OF  CARBON  AND  HYDRO- 
GEN, AND  THE  SIMULTANEOUS  VOLUMETRIC 
DETERMINATION  OF  NITROGEN,  IN  THE  ELE- 
MENTARY ANALYSIS  OF  ORGANIC  SUBSTANCES 

IF  the  combustion  of  substances  containing  nitro- 
gen be  carried  out,  not  in  tubes  filled  with  carbon 
dioxide  or  hydrogen,  as  in  the  methods  of  Dumas  and 
Bunsen,  but  in  complete  vacuum,  it  is  then  possible 
—  provided  that  after  the  combustion  the  tube  is  again 
exhausted  and  the  combustion  products  collected — to 
weigh  the  carbon  dioxide  and  water  and  to  measure 
the  nitrogen. 

In  addition  to  a  combustion  furnace,  a  tube  filled 
with  copper  oxide,  metallic  copper,  and  the  substance 
to  be  analysed,  and  absorption  apparatus  for  carbon 
dioxide  and  water,  the  method  to  be  described  calls 
for  an  air-pump  and  a  graduated  tube  for  measuring 
the  nitrogen. 

The  mercury  air-pump  constructed  by  Professor 
Topler1  possesses  neither  stopcocks  nor  valves  nor 
dead  space,  and  is  therefore  especially  suited  for  this 
work. 

This  air-pump  is  a  combination  of  three  barom- 
eters, two  of  which  act  as  valves,  while  the  third, 

i  Dingler's  Polyt.  Jour.,  163,  426  (1862). 
392 


CHAP,  xi      ANALYSIS   OF  ORGANIC   SUBSTANCES 


393 


analogous  to  the  Geissler  pump,  ends  in  a  thick-walled 
bulb  by  means  of  which  the  vacuum  is  produced. 
The  arrangement  is  shown  in 
Fig.  114. 

In  the  drawing,  ga  is  a  wide 
glass  tube  ending  in  the  glass 
bulb  A,  and  joined  by  a  wide 
rubber  tube  nf  with  the  large 
bulb  D.  From  the  upper  end 
of  A  &  narrow  bent  tube  qbc 
passes  downward  into  6r.  The 
length  of  this  last-named  tube, 
from  the  highest  point  b  to  the 
open  end  <?,  is  somewhat  more 
than  the  greatest  barometric 
height  of  the  locality. 

From  just  below  the  bulb  A 
rises  the  small  tube  as,  whose 
highest  point  is  considerably  more 
than  the  barometric  height  above 
the  highest  point  of  the  tube  qbc. 
At  s  this  tube  bends  downward 
again  and  is  permanently  con- 
nected with  the  receiver  B.  The 
whole  system  of  tubes  from  g  to  s  can  easily  be  put 
together  by  a  glassworker ;  it  is  fastened  to  a  suitable 
wooden  standard,  which  is  provided  at  different  levels 
with  supports  for  the  mercury  reservoir  D,  so  that  D 
can  easily  be  brought  into  any  desired  position. 

D  is  filled  with  mercury,  and  so  much  mercury  is 
poured  into  6r  that  the  end  of  be  is  about  1  cm. 
below  the  surface.  The  apparatus  is  then  ready  for 
use.  v 


FIG.  114. 


394  GAS  ANALYSIS  PART  in 

Regarding  the  use  of  the  apparatus,  a  discrimina- 
tion must  be  made  between  two  distinct  manipula- 
tions :  — 

1.  If  D  be  raised  to  the  height  of  the  bulb  A,  the 
air  in  the  latter  will  be  driven  out  by  the  mercury, 
and  will  escape  in  a  rapid  stream  of  bubbles  through 
the  mercury  in  6r.  By  raising  D  the  mercury  in  A 
is  brought  to  the  point  q.  When  no  more  bubbles 
escape  at  c,  D  is  brought  into  its  lowest  position,  as 
shown  in  Fig.  114.  The  mercury  in  A  sinks  rapidly, 
and  bubbles  of  air  enter  from  a  and  rise  through  A. 
When  the  mercury  in  ag  has  sunk  below  the  point 
a,  the  air  in  B  is  expanded  to  the  volume  A  +  B. 

At  the  same  time  the  mercury  in  the  vessel  6r, 
which  excludes  the  outer  air,  rises  slowly  in  the  tube 
be  to  a  height  which  corresponds  to  the  difference 
of  pressure.  By  again  raising  D  the  air  which  has 
passed  from  B  into  A  can  be  driven  out  at  <?,  the  open- 
ing a  being  meanwhile  closed  by  the  mercury  rising 
toward  A.  The  pressure  in  A  increases,  the  mer- 
cury in  be  falling  rapidly,  while  that  in  as  rises  above 
the  level  in  A.  It  is  obvious  that  the  sum  of  the 
two  columns  of  mercury  in  these  side  barometer  tubes 
is  at  every  moment  equal  to  the  difference  in  pressure 
between  the  expanded  air  in  B  and  the  atmosphere. 

When  the  level  of  the  mercury  in  A  has  again 
reached  <?,  the  simple  operation  of  raising  and  lower- 
ing D  is  repeated  until  no  air-bubbles,  or  only  insignifi- 
cant ones,  escape.  The  apparatus  may  be  compared 
to  the  piston  air-pump,  if  we  consider  the  barometer 
Ag  with  the  movable  vessel  D  as  the  cylinder,  the 
mercury  as  the  piston,  and  the  two  barometers  be 
and  as  as  the  valves. 


CHAP,  xi    ANALYSIS  OF  ORGANIC  SUBSTANCES  395 

In  the  above  manipulation  be  remains  filled  after 
each  stroke  with  air  at  the  pressure  of  an  atmosphere 
+  the  small  mercury  column  to  be  sustained  at  c. 
This  volume  of  air,  which  again  expands  into  A  when 
the  mercury  is  lowered,  constitutes,  in  a  manner,  the 
dead  space  of  the  air-pump. 

2.  By  a  simple  modification  of  the  manipulation, 
the  dead  space  may  also  be  exhausted,  after  the  ex- 
hausting in  B  has  gone  far  enough.  To  do  this,  the 
vessel  D,  at  the  end  of  each  stroke,  is  raised  so  high 
that  the  mercury  begins  to  flow  from  q  through  b 
toward  Gr.  If  the  dimensions  of  the  tube  be  have 
been  rightly  chosen,  it  fills  almost  instantly  with 
mercury,  the  air  being  completely  driven  out  at  c. 
If  D  be  now  brought  rapidly  into  its  lowest  position, 
there  is  formed  over  the  mercury  in  A  a  Torricellian 
vacuum  with  which  the  receiver  communicates  as 
soon  as  the  mercury  has  sunk  below  a.  It  is  clear 
that  by  repeating  this  last  proceeding,  the  exhaus- 
tion in  B  can  be  carried  to  any  desired  limit.  At 
the  first  stroke  thus  made  bubbles  of  air  are  seen  to 
ascend  in  A  from  a.  This  soon  ceases,  however,  if 
the  pumping  be  continued.  The  column  of  mercury 
in  be  now  stands  at  the  full  barometric  height  during 
the  whole  stroke,  and  only  at  the  moment  that  the 
opening  a  is  left  free  is  it  possible  to  discern,  from  a 
quick  jerk  of  the  mercury  in  be,  that  a  small  amount 
of  air  has  actually  passed  from  B  into  A.  This  jerk 
becomes  steadily  weaker  and  at  last  imperceptible. 

By  being  repeatedly  driven  over  at  b  the  amount 
of  mercury  in  D  would  constantly  decrease  and  would 
soon  stop  further  exhaustion,  unless  the  mercury  in  Gr 
were  poured  back  into  D.  Fortunately,  however,  the 


396  GAS  ANALYSIS  PART  in 

apparatus  itself  relieves  the  operator  of  this  trouble. 
If  the  tube  be  is  only  slightly  longer  than  the  baro- 
metric height,  then,  when  the  level  in  G-  has  been 
somewhat  raised  by  the  overflow  of  the  mercury,  the 
difference  of  level  between  G-  and  b  will  soon  become 
less  than  the  barometric  height.  Toward  the  end  of 
the  exhausting,  a  Torricellian  vacuum  is  formed  in  A 
at  the  beginning  of  every  stroke,  so  that  if  too  much 
mercury  has  passed  over  into  6r  it  now  flows  back  of 
itself  into  A,  and  in  a  short  time  the  level  in  Gr  is 
again  at  the  barometric  height  below  b. 

If  the  air  is  to  be  completely  driven  out  of  be,  the 
stream  of  mercury  must  hold  together  and  form  a 
column  which  wholly  fills  the  tube.  This  result  is 
easily  obtained  by  choosing  a  tube  of  not  more  than  2 
to  3  mm.  internal  diameter,  and  by  avoiding  irregular 
or  too  sharply  curved  bends.  It  is  also  well  to  have 
the  tube  q  widen  conically  where  it  joins  the  bulb  A. 

It  should  be  noted  that  after  the  apparatus  has 
been  completely  exhausted,  the  bottle  D  must  be 
brought  to  its  lowest  position  before  admitting  air 
into  the  receiver.  In  other  words,  the  mercury  in  ag 
should  stand  below  the  point  a,  for  otherwise  the  air 
entering  at  h  and  rushing  through  B  and  s  would 
throw  any  mercury  above  a  with  such  force  into 
the  empty  space  A  that  the  bulb  might  easily  be 
broken. 

It  is  advisable  to  fasten  the  air-pump  at  the  points 
a  and  n  by  larger  metal  bands,  the  space  between  the 
band  and  the  glass  being  filled  with  plaster  of  Paris. 
The  remaining  parts  of  the  apparatus  should  be  sup- 
ported by  fairly  wide  metal  bands  alone,  so  as  to  allow 
for  the  different  expansion  of  wood  and  glass. 


CHAP,  xi    ANALYSIS  OF  ORGANIC   SUBSTANCES  397 

It  is  clear  from  the  description  that  all  of  the 
sources  of  error  introduced  by  glass  stopcocks  and 
greased  joints  are  completely  avoided,  so  that  if  the 
receiver  B  is  tight  it  is  impossible  for  air  to  enter  the 
apparatus.  And  further,  in  the  second  manner  of 
operating  as  just  described,  the  layer  of  air,  which  in 
the  beginning  lies  between  the  mercury  and  the  glass 
because  of  the  incomplete  contact  between  the  last 
two,  is  gradually  driven  out  during  the  exhaustion,  so 
that  if  the  pumping  be  carried  on  long  enough,  there 
is  no  limit  to  the  attainable  exhaustion  of  air.  Much 
more  perfect  exhaustion  than  is  necessary  for  the 
analytical  methods  to  be  described  may  easily  be 
obtained  with  this  pump. 

To  carry  out  with  the  aid  of  this  air-pump  the 
simultaneous  determination  of  carbon,  hydrogen,  and 
nitrogen,  the  author  has  devised  the  form  of  appa- 
ratus and  pump  shown  in  Fig.  115. 

A  is  a  small  combustion  tube,  drawn  out  at  one 
end  to  a  bayonet  and  at  the  other  to  a  narrow  tube. 
B  is  a  calcium  chloride  tube,  to  the  front  side  of 
which  is  fused  a  small  bulb  apparatus  for  holding  a 
few  drops  of  concentrated  sulphuric  acid.  C  is  a 
soda-lime  tube.  D  is  the  air-pump ;  its  escape  tube  a 
is  bent  upward  at  c  in  the  small  mercury  trough  6r, 
so  that  a  graduated  tube  E  may  be  brought  over  its 
free  end.  The  gases  drawn  from  the  apparatus  by 
the  pump  must  then  pass  into  E  and  collect  there. 
The  end  c  of  the  escape  tube  is  fastened  into  a  hollow 
in  the  trough  by  pouring  molten  sealing-wax  around 
it.  The  screw-clamp  H  supports  the  movable  tube  J7, 
which  is  connected  with  the  trough  by  the  rubber 
tube  b  wrapped  in  linen.  The  apparatus  is  connected 


GAS   ANALYSIS 


PART  III 


at  d,  e,  and  /  by  pieces  of  new  black  rubber  tubing 
supplied  with  wire  ligatures. 

The  tube  A  is  first  drawn  out  at  g  to  a  thin  tube 
about  7  cm.  long.     It  is  then  thoroughly  dried  over 


ih   g 


FIG.  115. 


a  flame,  and  supplied  at  g  with  a  stopper  of  ignited 
long-fiber  asbestos.  (Short-fiber  asbestos  might  easily 
be  drawn  into  the  calcium  chloride  tube  during  the 
exhaustion.) 

The  tube  is  then  filled  from  g  to  h  —  5  to  8  cm.  — 
with  copper  powder,  from  h  to  i — 10  to  40  cm.,  de- 


CHAP,  xi    ANALYSIS  OF  ORGANIC  SUBSTANCES  399 

pending  on  the  nature  of  the  substance  to  be  analysed 
—  with  granular  copper  oxide,  from  i  to  k  with  a 
mixture  of  copper  oxide  and  the  substance,  and  from 
k  to  I  with  pure  copper  oxide.  At  I  a  stopper  of 
freshly  ignited  asbestos  is  inserted,  and  a  small  plati- 
num boat  containing  about  0.5  g.  potassium  chlorate 
is  pushed  in  after  it.  The  tube  is  now  drawn  out 
at  w,  in  the  blast-lamp  flame,  to  a  bayonet,  the 
smallest  space  possible,  about  5  cm.,  being  left  be- 
tween I  and  m. 

The  copper  powder  and  copper  oxide  are  brought 
close  together  in  the  tube,  and  no  canal  is  left,  the 
combustion  gases  being  thus  compelled  to  move 
through  the  whole  cross-section  of  the  tube. 

To  prepare  the  copper  powder,  coarse-grained 
sifted  copper  oxide  placed  in  a  small  combustion 
tube  is  reduced  with  hydrogen  at  low  red-heat.  The 
reduced  copper  is  then  ignited  and  allowed  to  cool 
in  a  stream  of  nitrogen.  This  latter  operation  is  most 
simply  performed  by  leading  1  to  1J  liters  of  dry 
air  over  the  copper  immediately  after  the  reduc- 
tion, and  while  the  tube  is  still  red-hot ;  in  fact,  it  is 
better  to  raise  the  temperature  somewhat.  The  oxy- 
gen of  the  air  will  oxidise  the  metallic  copper  lying 
next  the  point  of  entrance,  but  the  length  of  the 
layer  thus  oxidised  will  be  less  than  5  cm.  If  the 
layer  of  reduced  copper  oxide  is  about  15  cm.  long, 
there  is  thus  obtained  for  the  analysis  sufficient  cop- 
per powder  which  has  been  ignited  in  pure  nitrogen. 
The  powder  is  allowed  to  cool  in  a  slow  current  of 
air,  the  part  of  the  tube  where  the  air  enters  being 
kept  red-hot  for  a  short  time. 

The  hydrogen  used  for  the  reduction  must  be  freed 


400  GAS  ANALYSIS 


PART  III 


from  arsine,  stibine,  and  hydrocarbons  by  washing  it 
with  a  solution  of  potassium  permanganate. 

Copper  powder  thus  prepared  has  a  beautiful  me- 
tallic luster,  and  repeated  experiments  have  shown 
that  it  contains  no  trace  of  hydrogen.  The  forma- 
tion of  carbon  monoxide  from  the  carbon  dioxide, 
due  to  hydrogen  in  the  copper,1  does  not  occur  here ; 
no  water  is  formed  in  burning  the  copper  powder  to 
copper  oxide.  Copper  powder  made  in  this  manner 
is  an  exceptionally  good  reducing  agent,  even  at  a 
very  low  red-heat.  A  close  layer  5  to  8  cm.  long 
can  with  absolute  certainty  completely  decompose, 
even  in  a  vacuum,  the  nitric  oxide  resulting  from 
the  combustion  of  compounds  very  high  in  nitrogen. 
This  cannot  be  done  in  a  vacuum  with  the  ordinary 
copper  spirals. 

The  grains  of  sifted  copper  oxide  should  be  from 
1^  to  3  mm.  thick.  The  copper  oxide  is  prepared 
in  the  ordinary  manner,  is  freshly  ignited  before 
using,  and  is  allowed  to  cool  in  a  tightly  closed  pear- 
shaped  flask  with  narrow  neck. 

If  the  substance  to  be  analysed  is  a  solid,  it  is 
shaken  from  a  weighing  tube  into  the  combustion 
tube,  and  is  mixed  with  a  copper  oxide  by  means  of 
a  bent  wire. 

To  burn  liquids  of  any  boiling-point,  small  bulbs 
with  two  capillary  side  tubes  are  blown  from  a  thin 
glass  tube  (see  Fig.  116). 

By  sucking  with  the  mouth  at  c,  there  is  drawn  up 

into  b  a  small  amount  of  an  alloy  made  of  10  parts  of 

Wood's  metal  (50  parts  bismuth,  10  parts  cadmium, 

27  parts  lead,  and  13J  parts  tin),  and  2  to  3  parts 

1  Schrotter  and  Lautemann. 


CHAP,  xi     ANALYSIS   OF    ORGANIC    SUBSTANCES  401 

mercury.  This  alloy  solidifies  at  once  to  a  shining 
and  closely  adhering  thread  of  metal,  without  break- 
ing the  capillary  tube.  The  melting-point  of  this 
alloy  lies  between  50°  and  60°  C.,  quite  a  little  below 
that  of  Wood's  metal.  Moreover,  Wood's  metal 
alone  breaks  the  glass  walls  upon  solidifying. 


FIG.  116. 

When  the  glass  bulb  has  been  thus  prepared,  the 
end  c  is  cut  off  at  d,  and  the  other  end  is  cut  off  with 
the  nippers  until  the  thread  of  metal  is  from  1  to  2 
mm.  long.  The  tube  is  then  filled  through  d  (Fig. 
117)  with  the  liquid  to  be  analysed,  the  filling  being 
effected  by  warming  and  cooling  the  bulb  in  the 
usual  manner.  The  capillary  e  is  then  melted  to- 
gether at  d. 

The  use  of  a  glass  bulb  of  this  form  admits  of  ex- 
hausting the  combustion  tube  without  loss  of  the 


FIG.  117. 

substance  by  evaporation.  The  bulb  can  be  opened 
when  desired  by  gently  warming  the  end  of  the  cap- 
illary containing  the  alloy.  If  the  substance  is  very 
volatile,  this  capillary  is  given  a  length  of  from  10  to 
12  cm.,  so  that  when  the  end  is  warmed  the  liquid  in 
the  bulb  will  not  be  heated  to  boiling. 

The  author  has  found  it  easily  possible  with  the 
aid  of  this  bulb  to  analyse  nitrous  ether,  and  can  rec- 
ommend this  method  of  closing  the  bulb  for  deter- 
SD 


402  GAS   ANALYSIS  PART  in 

minations  of  vapour  density  as  well  as  for  the 
ordinary  analysis. 

In  vapour  density  determinations  by  Hofmann's 
method,  the  metals  of  Wood's  alloy,  may  be  disre- 
garded, for  the  whole  metal  stopper  weighs  only 
2  to  3  mg.  In  combustion  analyses  the  mercury  is 
stopped  by  the  wad  of  asbestos  in  the  end  of  the 
combustion  tube,  if  the  heat  is  not  raised  unneces- 
sarily high. 

A  small  boat  about  3  cm.  long,  made  by  bending 
a  piece  of  platinum  foil  into  the  desired  form,  serves 
to  hold  the  potassium  chlorate.  It  is  convenient  to 
measure  off  the  potassium  chlorate  in  a  small  glass 
tube  closed  at  one  end;  the  space  occupied  by  0.5  g. 
of  the  finely  pulverised  salt  is  noted  by  a  file  mark 
on  the  outside  of  the  tube. 

The  potassium  chlorate  is  heated  in  the  platinum 
boat  until  it  melts,  and  after  solidifying,  and  while 
still  hot,  it  is  pushed  into  the  combustion  tube. 

The  bayonet  of  the  tube  must  be  drawn  out  to  a 
very  fine  point,  so  that  it  may  be  easily  broken  off 
inside  a  rubber  tube  slipped  over  it. 

The  absorption  tubes  B  and  0  (Fig.  115  and  Fig. 
118)  are  filled  with  carefully  sifted  calcium  chloride 
and  soda-lime  (size  of  grains,  1^  to  3  mm.),  and  are 
closed  at  a  with  corks  and  carefully  sealed;  small 
bubbles  of  air  in  the  sealing-wax  may  be  removed 
with  a  hot  glass  rod.  At  b  and  c  (Fig.  118)  a  little 
cotton  is  tightly  inserted.  These  compact  stoppers 
of  cotton  are  sufficiently  porous,  and  the  resistance 
which  they  offer  to  the  passage  of  the  combustion 
gases  is  so  great  as  to  render  it  impossible  for  the 
gases  to  pass  through  the  apparatus  too  rapidly,  and 


CHAP,  xi     ANALYSIS   OF   ORGANIC    SUBSTANCES  403 

thus  escape  complete  absorption.  The  U-tubes 
should  be  quite  small  —  20  ccm.  capacity  for  each 
tube  is  sufficient  —  and  the  sulphuric  acid  in  the 
bulb  tube  and  the  soda-lime  should  be  renewed  after 
each  analysis.  The  calcium  chloride  may  be  used 
many  times. 

After  the  apparatus  has  thus  been  made  ready,  and 
the  absorption  tubes  weighed  and  carefully  connected, 
the  combustion  is  begun  by  first  placing  a  support 
under  the  calcium  chloride  tube  B  and  bringing  it 
into  a  horizontal  position,  as  shown  in  Fig.  119.  The 
sulphuric  acid  in  the  bulb  tube  passes  into  the  bulbs  a 


FIG.  118. 


and  yS,  the  air  in  the  combustion  tube  being  thus 
brought  into  direct  communication  with  the  air-pump. 
The  apparatus  is  then  carefully  exhausted.  If  the 
capacity  of  the  combustion  tube  and  the  absorption 
apparatus  is  small  in  comparison  with  that  of  the 
bulb  of  the  pump,  the  air  may  be  driven  out  of  the 
escape  tube  a  and  the  mercury  allowed  to  pass  over 
at  the  second  rising  of  the  mercury  reservoir.  The 
bulb  of  the  air-pump  should  be  of  about  500  ccm. 
capacity,  although  with  a  little  more  time  the  exhaus- 
tion may  be  made  equally  well  with  a  smaller  bulb. 
The  air-pump  used  by  the  author  in  his  experiments 
had  a  150  ccm.  bulb  made  from  a  large  pipette. 
Although  the  tubes  are  filled  with  copper  oxide, 


404 


GAS   ANALYSIS 


PART  IH 


calcium  chloride,  and  soda-lime,  the  volume  of  air 
which  they  still  contain  is  by  no  means  small.  It 
amounts  to  from  100  to  150  ccm.,  as  can  easily  be 
shown  by  placing  over  c  (Fig.  119)  in  the  mercury 
trough  a  measuring  tube  filled  with  mercury. 

When  the  air  in  the  apparatus  is  so  rarefied  that 
only  very  small   air-bubbles  escape   through  a,  the 


FIG.  119. 


combustion  tube  is  heated  to  glowing  at  Z,  and  the 
oxygen  of  the  potassium  chlorate  is  thus  set  free. 
The  oxygen  displaces  the  air  in  the  apparatus  and 
detaches  the  layer  of  air  adhering  to  the  large  sur- 
face of  the  powdered  substances  —  an  operation 
which  many  experiments  have  shown  should  never 
be  omitted.  The  apparatus  is  again  exhausted,  and 
when  only  very  small  air-bubbles  pass  over,  the  cop- 
per powder  between  g  and  h  is  brought  to  red-heat. 
The  metallic  copper  unites  with  the  oxygen  in  the 


CHAP,  xi     ANALYSIS   OF   ORGANIC   SUBSTANCES  405 

tube,  so  that,  by  further  pumping,  the  point  is  soon 
reached  at  which  only  extremely  small  bubbles  escape 
through  a.  The  apparatus  is  then  sufficiently  ex- 
hausted ;  the  oxygen  remaining  in  the  tubes  has  no 
effect  upon  the  accuracy  of  the  results. 

The  calcium  chloride  tube  is  now  placed  upright, 
and  the  substance  is  burned  in  the  usual  manner.  It 
is  advisable  to  lay  the  combustion  tube  in  a  trough 
consisting  of  several  pieces,  and  to  regulate  the  heat 
with  small  asbestos  screens.  The  tubes  can  be  used 
several  times  if  the  heat  rises  only  to  a  dark  red,  this 
sufficing  for  complete  combustion. 

The  progress  of  the  combustion  may  be  judged  by 
the  rapidity  with  which  the  gas  passes  through  the 
sulphuric  acid  in  the  drying  tube,  and  by  the  heating 
of  the  soda-lime  tube  caused  by  the  absorption  of  the 
carbon  dioxide  ;  not  more  than  half  of  the  soda-lime 
tube  should  become  warm. 

Small  amounts  of  gas  take  up  a  great  deal  of  space 
in  chambers  which  are  nearly  exhausted,  and  for  this 
reason  the  passage  of  the  gas  through  the  sulphuric 
acid  is  at  first  quite  violent.  For  this  reason  it  is 
advisable  and  sometimes  necessary,  if  the  substance  is 
not  explosive,  to  close  the  end  c  of  the*  escape  tube  a 
during  the  combustion,  and  to  raise  the  mercury  reser- 
voir J  (Fig.  115)  to  the  height  of  the  bulb  of  the  air- 
pump.  The  pump  is  thus  filled  with  mercury,  and 
the  evolved  gases  soon  produce  a  certain  pressure 
within  the  combustion  tube  and  the  absorption  appa- 
ratus. The  amount  of  this  pressure  can  be  told  from 
the  position  of  the  mercury  in  the  tube  o,  and  can 
be  regulated  by  raising  or  lowering  the  mercury 
reservoir. 


406 


GAS   ANALYSIS 


PART  IH 


The  end  of  c  is  closed  with  a  conical  glass  tube 

lined  with  rubber.1 

The  tube  is  closed  at  the  upper  end  and  fastened 

into  a  wooden  rod  with  sealing-wax  If  this  cap  be 
pressed  down  upon  the  mouth  of 
c  by  means  of  a  clamp,  as  shown 
in  Fig.  120,  the  tube  is  completely 
closed. 

When  the  combustion  is  ended 
the  cap  is  removed,  and  the  grad- 
uated tube  E  (Fig.  119)  is  placed 
over  c.  E  must  always  be  moist- 
ened near  the  stopcock  with  a 
drop  of  water.  The  tube  F  which 
is  connected  with  the  mercury 
trough  by  the  rubber  tube  b  is 
used  for  rilling  the  graduated 
tube.  A  single-bore  rubber  stop- 
per fitting  the  graduated  tube  is 
fastened  into  the  bottom  of  the 
mercury  trough  (see  Fig.  120) 
with  sealing-wax.  The  rubber 
tube  b  is  fastened  to  the  glass 
tube  which  passes  through  the 
stopper.  If  the  graduated  tube 
be  pressed  down  firmly  over  the 
rubber  stopper,  it  can  be  easily 
filled  with  mercury  by  raising 
the  tube  F.  And,  further,  by 
bringing  the  tubes  E  and  F  into 

the  position  shown  in  Fig.  119,  a  gas  confined  in  the 

measuring  tube  may  be  brought  under  atmospheric 

1  Bunsen,  Gasometrische  Methoden,  2d  ed.,  p,  161, 


FIG.  120. 


CHAP,  xi     ANALYSIS  OF  ORGANIC  SUBSTANCES  407 

pressure  and  measured,  the  correction  for  difference 
of  level  of  the  mercury  in  tube  and  trough  being 
thus  avoided. 

Graduated  tubes  of  this  form,  supplied  with  a  glass 
stopcock  and  holding  from  75  to  100  ccm.,  are  very 
convenient  for  collecting  the  gas  in  the  Dumas  method 
for  determining  nitrogen,  or  in  the  Schulze  determi- 
nation of  nitric  acid ;  they  can  easily  be  filled  with 
sodium  hydroxide  solution  by  applying  suction  at 
the  upper  end,  and  the  troublesome  inverting  of 
the  tubes  is  thus  avoided. 

After  the  combustion,  the  nitrogen  in  the  tube  and 
the  absorption  apparatus  is  drawn  over  into  the 
graduated  tube  by  means  of  the  air-pump.  The 
exhausting  is  continued  until  only  extremely  small 
bubbles  pass  over.  It  denotes  no  error  if  later  a 
passage  of  gas  is  shown  by  a  periodic  movement 
of  the  sulphuric  acid  in  the  calcium  chloride  tube, 
for  this  is  caused  by  the  small  quantity  of  gas 
which  is  still  in  the  tubes  and  which  is  disregarded 
in  the  analyses.  It  is  advisable  to  exhaust  slowly, 
for  the  gases  need  a  certain  time  to  move  through 
the  capillary  spaces  in  the  asbestos  and  cotton  stop- 
pers. 

When  the  exhausting  is  ended,  E  is  placed  as  in 
Fig.  119.  A  thin  rubber  tube,  which  is  closed  in  the 
middle  with  a  screw  pinchcock,  is  slipped  over  the 
bayonet,  and  the  point  of  the  latter  is  broken  off  in- 
side of  the  tube.  To  burn  any  carbon  which  may 
have  separated,  dry  oxygen  is  led  through  the  tube 
until  the  metallic  copper  begins  to  oxidise.  The 
carbon  dioxide  and  oxygen  are  then  displaced  by  air ; 
the  current  of  gas  can  be  regulated  as  desired  by 


408 


GAS  ANALYSIS 


PART  III 


raising  or  lowering  the  mercury  reservoir  of  the 
air-pump. 

The  apparatus  is  then  disconnected,  and  after  it 
has  assumed  the  temperature  of  the  balance  room, 
it  is  weighed.  The  nitrogen  is  measured  and  its 
weight  is  calculated,  with  due  allowance  for  tempera- 
ture, barometric  pressure,  and  the  tension  of  aqueous 
vapour. 

This  method  takes  about  as  much  time  as  the 
Dumas  determination  of  nitrogen.  It  is  especially 
valuable  for  the  analysis  of  explosive  compounds,  for 
the  change  in  pressure  causes  a  change  in  the  boiling- 
point.  For  example,  nitro-glycerin  can  be  burned 
and  distilled  in  a  vacuum,  without  explosion  result- 
ing ;  this  cannot  be  done  under  ordinary  atmospheric 
pressure. 

ANALYSES 


Analysis  of  Aniline 

Found 


Calculated 


I 

II 

III 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Carbon 

.       77.3 

77.9 

77.4 

77.4 

Hydrogen     . 

7.6 

7.8 

8.8  1 

7.5 

Nitrogen 

.       14.8 

15.0 

14.9 

15.0 

Amount  of  sub- 

stance  taken         0.2689  g.      0.1154  g.      0.1089  g. 


Asbestos  passed  over  into  the  calcium  chloride  tube. 


CHAP,  xi     ANALYSIS   OF   ORGANIC   SUBSTANCES 


409 


Analysis  of  Picric  Acid 

Found 


Calculated 


I 

II 

III 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

31.3 

31.7 

31.1 

31.4 

2.4  l 

1.6 

1.5 

1.3 

17.9 

18.3 

18.1 

18.3 

Carbon 
Hydrogen     . 
Nitrogen 
Amount  of  sub- 
stance taken          0.1785  g.        0.164  g.      0.3333  g. 


Analysis  of  Nitro-glycerin 

Found 


Calculated 


I  II  III  IV 

Per  cent      Per  cent      Per  cent      Per  cent      Per  cent 

Carbon          .  15.6  15.7  15.7  16.3           15.8 
Hydrogen      .          2.6             2.9             2.4  2.3  2.2 
Nitrogen       .  18.5  18.8  18.9  18.7           18.5 
Amount  of  sub- 
stance taken  0.144  g.  0.210  g.  0.2803  g.  0.3620  g. 

If,  in  pumping  out  the  apparatus,  the  exhaustion 
is  carried  equally  far  both  before  and  after  the 
combustion,  the  volumes  of  gas  remaining  in  the 
tubes  must  be  in  both  cases  the  same,  and  no 
errors  in  the  analysis  would  result,  provided  that 
these  residual  gases  had  within  certain  limits  the 
same  composition.  But  at  the  beginning  the  com- 
bustion tube  is  filled  with  air,  while,  after  the  com- 
bustion, it  contains  a  mixture  of  water  vapour,  carbon 
dioxide,  and  nitrogen,  in  which  the  amount  of  nitro- 
gen is  very  small  in  the  greater  number  of  cases. 
For  this  reason  the  nitrogen  result  would  be  too 
1  See  note,  p.  408. 


410  GAS  ANALYSIS  PART  in 

high  if  the  tube  were  not  filled  with  oxygen  as  above 
described,  for  there  remains  after  the  first  exhaustion 
a  certain  quantity  of  air,  high  in  nitrogen,  which 
would  be  displaced  by  the  gases  evolved,  while  after 
the  combustion  a  gas  mixture  low  in  nitrogen  results. 
Aside  from  the  fact  that  the  greatest  vacuum  possible 
may  be  obtained  by  filling  a  space  with  absorbable 
gases  and  then  absorbing  these  gases,  the  errors 
which  might  result  from  incomplete  exhaustion  are 
equalised  if  oxygen  is  set  free  as  described ;  for  this 
oxygen  cannot  escape  from  the  tube,  but  on  the 
contrary  is  taken  up  by  the  metallic  copper. 

In  the  analysis  of  nitro-glycerin  the  resulting  mix- 
ture of  water  vapour,  carbon  dioxide,  and  nitrogen 
contains  a  large  amount  of  the  last-named  substance. 
For  this  reason  the  evolution  of  oxygen  may  be 
omitted  if  the  combustion  be  made  in  a  short  tube 
about  20  cm.  long.  Moreover,  nitro-glycerin  does 
not  evaporate  to  any  extent  at  ordinary  temperatures 
in  a  vacuum,  so  that  the  substance  may  be  weighed 
in  a  boat  and  mixed  directly  with  the  copper  oxide. 
A  layer  of  copper  powder  about  6  cm.  long  is  brought 
into  the  combustion  tube,  then  a  layer  of  copper  oxide 
of  about  the  same  length,  the  boat  is  introduced,  the 
tube  filled  with  copper  oxide  and  drawn  out  to  a 
bayonet.  The  tube  is  then  exhausted  as  completely 
as  possible  and  is  slowly  brought  to  a  red-heat,  the 
heating  beginning  at  the  metallic  copper.  The  rest 
of  the  operation  is  like  that  already  described. 

Even  with  a  pressure  of  290  mm.  inside  the 
combustion  tube,  the  nitro-glycerin  burned  without 
explosion  in  my  analyses. 


CHAPTER   XII 

A   CALORIMETRIC   METHOD   FOR   THE   DETERMINA- 
TION OF  THE  HEATING  POWER  OF  FUEL 

IN  connection  with  an  extended  series  of  experi- 
ments upon  the  action  of  furnaces  constructed  for 
the  smokeless  consumption  of  coal,  the  author  was 
led  to  look  up  the  calorimetric  determination  of  the 
heating  power  of  fuels.  An  attempt  was  first  made 
to  work  with  the  calorimeter  constructed  by  F. 
Fischer,  but  it  was  soon  found  that  under  the  given 
conditions  the  determinations  could  not  be  carried 
out  with  this  apparatus.  In  the  investigation  in 
question,  the  coals  were  in  the  form  of  very  fine 
powder  resulting  from  the  taking  of  an  average 
sample  from  a  large  amount  of  coal  (see  below). 

Although  many  varied  experiments  were  tried,  it 
was  impossible  to  burn  the  coal  so  that,  excepting 
the  ash,  only  gaseous  products  would  result:  some 
tar  was  always  formed.  The  endeavour  to  obtain  a 
combustion  without  the  formation  of  tar,  by  pressing 
the  coal  dust  into  solid  pieces  (as  later  described), 
and  by  intermixture  of  indifferent  substances,  such 
as  infusorial  earth,  led  to  no  desirable  results.  Start- 
ing with  the  idea  that  the  preference  must  be  given 
to  that  method  which  would  afford  a  perfectly  com- 
plete combustion,  the  author  subjected  the  method 
of  Berthelot 1  to  a  careful  experimental  examination, 

1  Compt.  rend.,  91,  188. 
411 


412  GAS   ANALYSIS  PART  m 

and  found  that  it  was  actually  possible  to  burn  coal 
with  an  excess  of  oxygen  and  under  high  pressure, 
directly  to  ash,  carbon  dioxide,  water,  and  nitrogen. 

The  combustion  was  made  in  an  autoclave  of  such 
a  shape  that  a  beaker  could  be  placed  inside  of  it. 
Beyond  this,  the  manipulation  was  the  same  as  that 
described  in  detail  later.  The  products  of  combus- 
tion were  first  passed  through  a  calcium  chloride 
tube,  and  a  Liebig  potash  bulb  with  caustic  potash 
tube,  then  through  a  red-hot  tube  containing  copper 
oxide,  and  again  through  a  calcium  chloride  tube 
and  a  Liebig  potash  bulb  with  caustic  potash  tube. 

In  all  cases  there  was  no  trace  of  tar  in  the  beaker 
within  the  autoclave;  the  coal  was  burned  com- 
pletely, and  the  ash  was  fused  to  a  glassy  slag.  A 
Saxon  coal  was  used  in  the  experiments. 

1.  0.5  g.  of  coal  burned  in  an  autoclave  of  300 
ccm.    capacity,    under   a   pressure   of   6  kg.   to   the 
square   centimeter,  gave   0.0045  g.    carbon  dioxide 
and    0.013   g.    water   in    the    incompletely   burned 
products  of  the  combustion. 

2.  1  g.  of  coal  burned  in  an  autoclave  of  300  ccm. 
capacity,  under  a  pressure  of   8  kg.   to  the  square 
centimeter,  gave  0.105  g.  carbon  dioxide  and  0.0086  g. 
water  in  the  incompletely  burned  products  of  the 
combustion. 

3.  0.779  g.  of  coal  was  burned  in  an  autoclave  of 
260  ccm.  capacity  under  a  pressure  of  16  kg.  to  the 
square  centimeter.      The  weight  of  the  last  potash 
bulb  was  — 

Before  the  experiment,  64.077  g. 
After     "  "  64.077  g. 


CHAP,  xii       THE   HEATING  POWER   OF   FUEL  413 

4.  0.652  g.  of  coal  was  burned  in  an  autoclave  of 
260  ccm.  capacity,  under  a  pressure  of  12  kg.  to  the 
square  centimeter.     The  weight  of  the  last  potash 
bulb  was  — 

Before  the  experiment,  64.077  g. 
After     "  "  64.076  g. 

5.  0.835  g.  of  coal  was  burned  in  an  autoclave 
of  260  ccm.  capacity,  and  under  a  pressure  of  12  kg. 
to  the  square  centimeter.     The  weight  of  the  last 
potash  bulb  was  — 

Before  the  experiment,  64.076  g. 
After     "  "  64. 0775  g. 

6.  0.9878  g.  of  coal  was  burned  in  an  autoclave 
of  260  ccm.  capacity,  and  under  a  pressure  of  12  kg. 
to  the  square  centimeter.     The  weight  of  the  last 
potash  bulb  was  — 

Before  the  experiment,  64.077  g. 
After     "  "  64.077  g. 

These  experiments  show  that  in  an  apparatus  of 
about  ^  liter  capacity,  1  g.  of  coal  can  be  completely 
burned  in  an  atmosphere  of  oxygen  under  a  pressure 
of  12  kg.  to  the  square  centimeter. 

It  cannot  be  denied  that  working  with  a  pressure 
of  several  atmospheres  entails  certain  inconveniences. 
Nevertheless,  the  author  is  of  the  opinion  that  the 
preference  must  be  given  to  the  Berthelot  method 
above  all  others,  because,  on  the  one  hand,  the  total 
products  of  the  combustion  remain  in  the  calorimeter, 
thus  admitting  of  a  simple  and  direct  measurement 


414  GAS  ANALYSIS  PART  m 

of  the  heat  without  any  calculation,  while,  on  the 
other  hand,  complete  combustion  is  attained. 

After  many  unsuccessful  experiments  the  author 
has  finally  succeeded  in  modifying  the  Berthelot 
method  so  that  coal  in  the  form  of  dust  can  easily  be 
burned,  and  he  has  devised  an  apparatus  with  which 
the  experiment  can  be  successfully  performed  with 
the  aid  of  simple  appliances. 

The  combustion  is  made  in  an  apparatus  similar  to 
that  proposed  by  Berthelot.  The  coal  is  pressed  into 
solid  pieces  in  a  steel  form l  by  means  of  an  ordinary 
screw-press,  is  then  electrically  ignited,  and  is  burned 
under  a  pressure  of  12  kg.  to  the  square  centimeter 
(11.6  atmospheres). 

The  object  of  the  technical  examination  of  coal 
is  to  determine  the  average  value  of  a  large  mass  of 
fuel,  so  that  to  obtain  accurate  results  it  is  necessary 
that  an  average  sample  be  selected  with  great  care. 
To  do  this  a  whole  car-load  of  coal  is  spread  out  in  a 
flat  heap,  the  coal  is  taken  out  in  parallel  furrows 
with  a  shovel.  The  coal  thus  obtained,  which  should 
amount  to  several  hectoliters,  is  broken  up  to  the  size 
of  hazel  nuts  with  an  ordinary  hand  stamp,  again 
spread  out  in  a  flat  heap,  and  coal  is  taken  from  as 
many  different  places  as  possible  in  the  heap  until 
5  kg.  is  thus  obtained.  The  coal  is  weighed  on  an 
ordinary  balance  with  an  exactness  of  about  1  g. 
and  is  then  allowed  to  lie  exposed  to  the  air  on  a 
large  sheet  of  paper  until  the  difference  between 
two  readings  made  after  an  interval  of  about  six 
hours  does  not  amount  to  more  than  20  g.  The 

1  In  his  calorimetric  experiments,  Stohmann  used  solid  pieces 
formed  in  a  similar  manner. 


CHAP,  xii       THE   HEATING  POWER  OF   FUEL  415 

amount  of  moisture  thus  found  is  termed  "mine 
moisture."  The  air-dried  coal  is  then  ground  to  a 
fine  powder  in  a  ball-mill.  In  this  way  we  get 
a  sample  which  represents  sufficiently  well  the 
average  composition  of  the  coal  in  question. 

Although  it  is  very  convenient,  for  all  other 
analyses,  to  have  the  coal  in  finely  pulverised  con- 
dition, this  is  quite  undesirable  in  the  calorimetric 
determination.  If  we  attempt  to  burn  coal  dust  in 
a  current  of  oxygen,  the  coal  dust  lying  upon  a 
sheet  of  asbestos  paper,  tar  is  always  formed  in 
addition  to  the  gaseous  combustion  products,  if  the 
coal  is  highly  bituminous;  in  some  cases  a  separa- 
tion of  soot  was  observed.  Moreover,  the  coal  dust 
cannot  be  used  direct  in  the  Berthelot  apparatus, 
because  the  combustion  is  there  made  in  a  basket  of 
platinum  wire-gauze. 

This  difficulty  can  be  avoided  by  exposing  the 
coal  dust  to  high  pressure  and  thus  forming  it  into 
a  small  cylinder  through  which  passes  a  piece  of 
thread  for  igniting  the  coal.  The  arrangement  shown 
in  Figs.  121  and  122  is  used  for  this  purpose.  This 
consists  of  a  small,  four-cornered  steel  form  (Fig. 
121),  which  can  be  inserted  into  a  small  screw-press 
(Fig.  122).  The  projections  on  the  side  of  the  block 
play  in  slits  in  the  frame  of  the  press. 

Through  the  block  of  steel  is  a  cylindrical  slot 
which  is  conically  widened  at  the  lower  end.  In 
this  conical  space  is  inserted  the  piece  6,  which  has 
the  form  of  a  truncated  cone.  The  surface  of  b  has 
on  two  sides  shallow  channels  in  which  is  laid  the 
piece  of  thread  that  is  to  pass  through  the  coal  cylin- 
der when  this  is  made  by  pressure  (see  Fig.  121). 


416 


GAS  ANALYSIS 


PART  III 


The  piece  of  thread  should  be  about  10  cm.  long,  and 
after  it  has  been  laid  along  the  channels  of  the  bot- 
tom piece  b  the  latter  is  inserted  into  the  lower  end 
of  the  opening  of  a.  About  1.2  g.  of  powdered  coal 
is  then  shaken  into  the  upper  end  of  the  opening,  the 
short  steel  cylinder  c  is  inserted,  and  the  steel  plunger 
d  is  placed  in  the  upper  end  of  the  opening.  The 
block  is  then  slid  into  the  press  (see  Fig.  122),  care 

being  taken  that  the 
thread  does  not  slip 
out  of  position  and 
that  it  lies  in  the  chan- 
nels in  the  steel  block, 
for  otherwise  it  might 
be  cut  off  when  the 
pressure  is  applied. 
This  cutting  of  the 
thread  can  be  easily 
avoided  by  fastening 
its  outer  ends  into  po- 
sition with  small  bits 
of  wax.  The  ends  of 
the  thread  which  have 

come  into  contact  with  the  wax  can  afterward  be  cut 
off,  and  any  error  which  might  arise  from  the  pres- 
ence of  particles  of  wax  in  the  combustible  substance 
can  thus  be  avoided.  A  piece  of  thread  of  a  length 
of  100  mm.  weighs  only  2J  mg.,  so  that  simply  meas- 
uring the  length  of  the  piece  employed  is  sufficient 
to  exactly  determine  its  weight  if  the  weight  of  a  long 
piece  of  the  thread  has  previously  been  determined 
once  and  for  all. 

The  screw  of  the  press  is  now  turned  down,  and 


PIG.  121. 


CHAP,  xii       THE   HEATING  POWER  OF  FUEL 


417 


with  moderate  pressure  the  coal  dust  is  compressed 
into  a  compact,  adherent  cylinder.  The  screw  is 
then  turned  up,  the  form  is  withdrawn  from  the 
lower  guides,  the  ends  of  the  thread  where  they 
have  come  into  contact  with  the  wax  are  cut  off 
with  a  knife,  and  the  form  is  slipped  into  the  upper 


FIG.  122. 

guides  of  the  press.  On  again  turning  down  the 
screw,  the  coal  cylinder  is  pushed  down  through  the 
form. 

The  form  should  be  carefully  cleaned  after  use  and 
thoroughly  oiled.  An  excess  of  oil  is  removed  with 
filter  paper.  A  trace  of  oil  is  intentionally  left  in 
the  form,  since  it  greatly  facilitates  the  preparation 
of  the  coal  cylinders. 


418 


GAS  ANALYSIS 


PART  III 


The  coal  cylinder  thus  prepared  is  freed  from 
adhering  coal  dust  and  loose  particles  of  coal  by 
means  of  a  small  camel's-hair  brush,  and  the  upper 
part  of  the  cylinder  is  cut  off  with  a  knife  until  the 
remaining  piece  through  which  the  thread  passes 

weighs  about  1  g.  The 
sample  is  then  placed  upon 
a  watch-glass,  covered  and 
accurately  weighed. 

The  combustion  is  car- 
ried out  in  an  autoclave 
of  the  form  shown  in  Fig. 
128.  The  autoclave  is 
turned  out  from  a  piece 
of  soft  cast  iron,  and  is 
enamelled  on  the  inside. 
It  is  unnecessary  to  use 
steel,  for  it  is  easy  to  make 
vessels  of  cast  iron  which 
will  withstand  a  pressure 
of  several  hundred  atmos- 
pheres, even  when  the 
walls  are  no  thicker  than 
5  mm.  Moreover,  a  piece 
of  apparatus  made  from 
soft  cast  iron,  if  it  gives  way  under  high  pressure, 
does  not  explode  but  simply  cracks  open,  and  the 
operator  is,  therefore,  not  exposed  to  the  possibility 
of  serious  injury  if  the  autoclave  bursts. 

The  autoclave  consists  of  the  vessel  A  and  the 
piece  B  which  is  screwed  into  the  neck  of  A.  The 
joint  is  made  perfectly  tight  by  means  of  washers  of 
vulcanite  or  lead.  Two  vertical  openings  a  and  b 


FIG.  123. 


CHAP,  xii        THE   HEATING  POWER   OF  FUEL  41& 

pass  through  the  head  B.  The  opening  a  can  be 
closed  gas  tight  by  means  of  the  screw  valve  passing 
through  c.  Vulcanite  is  also  used  as  packing  for  the 
stuffing  box  of  this  valve.  Just  above  the  valve  seat 
is  a  horizontal  opening  which  ends  in  the  tube  d. 
The  opening  b  is  slightly  conical  in  form.  Through 
it  passes  a  metal  rod  e  which  is  slightly  widened  at 
one  point  and  is  fitted  air-tight  into  the  opening  by 
means  of  a  piece  of  rubber  tubing  2J  mm.  in  internal 
diameter  with  a  wall  1  mm.  thick,  e  is  easily  inserted 
in  place  by  first  drawing  through  the  conical  opening 
a  fairly  long  piece  of  rubber  tubing  by  attaching  to 
the  end  of  the  tubing  a  piece  of  wire,  and  then  shov- 
ing the  lower  end  of  the  rubber  tube  over  e  until  it 
projects  a  few  centimeters  beyond  the  thickened  part 
of  the  wire.  Upon  taking  hold  of  both  ends  of  the 
rubber  tube  and  stretching  it,  it  is  easy  to  push  e  and 
the  rubber  tube  into  the  conical  opening  to  such  an 
extent  that  tight  contact  is  made  at  the  thickened 
part  of  the  wire  when  the  rubber  is  released.  When 
this  has  been  done,  the  lower  end  of  the  tube  is 
drawn  down  out  of  the  opening  and  cut  off  with  a 
sharp  knife.  The  rubber  tube  then  draws  back 
into  the  opening  to  such  an  extent  that  its  end  is 
from  10  to  20  mm.  from  the  mouth  of  the  opening. 
To  completely  protect  the  rubber  from  the  action 
of  the  products  of  combustion,  the  space  between  e 
and  the  sides  of  the  conical  opening  through  the 
head  is  tightly  packed  with  long-fibered  asbestos. 
/  is  a  thick  iron  wire  fastened  into  the  head  B.  To 
its  lower  end  and  to  the  lower  end  of  e  are  fastened 
two  pieces  of  platinum  wire  about  1  mm.  in  diameter, 
and  these  are  connected  across  directly  below  the  ends 


420  GAS   ANALYSIS  PART  in 

of  the  iron  wires  by  a  very  fine  platinum  wire  g. 
The  lower  ends  of  the  two  heavy  platinum  wires  are 
bent  upward  in  the  form  of  hooks,  and  upon  these 
hooks  is  suspended  by  means  of  two  loops  of  plati- 
num wire  a  small  basket  of  chamotte. 

For  the  purpose  of  igniting  the  coal,  a  cap  is 
placed  over  the  head  of  the  valve  screw  ^,  and 
another  one  over  the  upper  end  of  the  insulated  rod 
e  at  z,  and  to  these  caps  are  fastened  brass  rods 
about  15  cm.  long.  It  is  well  to  draw  a  thin  rubber 
tube  over  the  brass  rod  which  is  attached  to  i,  so  as 
to  completely  insulate  it.  The  rods  are  connected 
with  the  poles  of  a  Bunsen  dip  battery  or  other 
source  of  current  by  means  of  ordinary  binding 
clamps  and  wires. 

Before  using  the  bomb  the  operator  should  deter- 
mine the  strength  of  current  necessary  to  bring  the 
thin  platinum  wire  g  to  glowing  without  melting  it. 
If  a  dip  battery  is  employed,  it  is  sufficient  to  simply 
note  the  depth  to  which  the  plates  of  the  battery 
must  be  lowered  in  order  to  obtain  a  current  just 
sufficient  to  properly  heat  the  wire.  The  headpiece 
is,  of  course,  not  inserted  in  place  in  the  bomb  when 
the  wire  is  thus  tested. 

The  thread  passing  through  the  coal  cylinder  is 
grasped  by  a  small  pair  of  pincers,  and  the  coal  is 
placed  in  the  chamotte  basket,  the  basket  itself 
being  suspended  on  a  weighed  watch-glass,  so  that 
any  particles  of  coal  which  may  be  detached  from 
the  cylinder  will  fall  upon  the  glass.  The  weight  of 
these  particles  is  then  determined  and  subtracted 
from  the  weight  of  the  coal  cylinder.  The  head- 
piece of  the  bomb  is  then  placed  in  a  support  (the 


CHAP,  xii       THE   HEATING  POWER   OF  FUEL 


421 


ring  of  a  retort  stand  will  answer),  and  one  end  of 
the  thread  is  tied  to  the  thin  platinum  wire  g,  all 
other  parts  of  the  thread  being  cut  off,  and  their 
weight  determined  by  measuring  their  length. 

The  autoclave  is  now  closed,  care  being  taken  to 
shake  the  chamotte  basket  as  little  as  possible,  and 
to  thereby  avoid  detaching  from  the  cylinder  par- 
ticles of  coal  which  would  fall  to  the  bottom  of  the 
autoclave  and  escape  combustion. 

The  headpiece  of  the  autoclave  should  be  tightly 
screwed  into  position  with  the  aid  of  a  long-handled 
wrench,  the  auto- 
clave being  held 
firmly  by  placing 
it  in   a   cylinder 
shown     in     Fig. 
124.     This  cylin- 
der is  bolted  to  a 
table,    and   has 

through   its   bot-  FlG>  124> 

torn  three    open- 
ings, which  correspond  to  three  feet  projecting  from 
the  bottom  of  the  bomb. 

When  the  autoclave  has  been  closed,  the  tube  d, 
projecting  from  the  side  of  the  head,  is  connected 
with  a  branch  tube  carrying  at  one  end  a  small  ma- 
nometer b  (Fig.  125),  and  joined  at  the  other  end  to 
a  cylinder  containing  compressed  oxygen. 

The  valve  o  (Fig.  125)  is  now  opened  by  giving 
the  spindle  half  a  revolution  to  the  left,  and  the 
valve  of  the  oxygen  cylinder  is  then  carefully  opened 
and  the  pressure  in  the  bomb  is  allowed  to  rise  to 
about  5  atmospheres,  The  oxygen  cylinder  is  then 


422 


GAS  ANALYSIS 


PART  III 


closed,  and  the  connection  at  d  is  slightly  opened,  so 
as  to  allow  the  gas  in  the  bomb  to  escape.  The 
larger  part  of  the  air  originally  present  in  the  appa- 
ratus is  thus  removed.  The  bomb  is  again  tightly 
connected  up  at  d,  and  the. oxygen  cylinder  opened 
until  the  pressure  has  slowly  come  up  to  15  atmos- 
pheres. The  cylinder 
is  then  shut  off,  and  the 
valve  o  is  closed.  The 
autoclave  is  discon- 
nected at  d,  and  is 
placed  for  a  moment  in 
a  beaker  of  water,  to  as- 
certain whether  it  is 
completely  tight.  If 
gas  bubbles  escape  from  the  valve,  or 
around  the  joint  between  the  headpiece 
and  the  body  of  the  bottom,  the  screws 
must  be  turned  down  tighter  until  no 
leakage  can  be  noticed.  If  this  leakage 
cannot  be  stopped  by  tightening  the 
screws,  the  washers  must  be  renewed, 
and  the  face  of  the  valve  must  be  re- 
ground. 

If  compressed  oxygen  is  not  at  one's 
disposal,  the  autoclave  can  be  filled  by  means  of  a 
retort  made  from  a  bent  iron  tube  (see  Fig.  126). 
This  tube  is  filled  with  40  g.  of  a  mixture  of  equal 
parts  of  manganese  dioxide  and  potassium  chlorate. 
It  is  connected  with  the  autoclave  in  the  manner 
shown  in  the  figure.  The  two  flanges  at  a  are  fastened 
together  by  small  bolts,  with  a  lead  washer  between 
the  flanges.  The  manometer  b  and  autoclave  B  are 


FIG.  125. 


CHAP,  xii        THE   HEATING   POWER   OF  FUEL  423 

placed  in  a  cylinder  of  water,  to  enable  one  to  see 
at  a  glance  whether  the  apparatus  is  wholly  tight. 
The  upper  part  of  the  retort  A  is  first  heated  with 
the  full  flame  of  a  free-burning  Bunsen  burner,  and 
this  heating  is  discontinued  when  the  manometer 
shows  a  pressure  of  1  atmosphere.  The  hot  iron 
tube  still  contains  heat  sufficient  to  set  free  enough 
oxygen  to  bring  the  pressure  up  to  6  atmospheres. 
'By  loosening  the  connection  at  a  the  pressure  is 
allowed  to  fall  until  the  manometer  stands  at  zero. 


FIG.  126. 

Tight  connection  is  then  again  made,  and  A  is  care- 
fully heated  until  the  manometer  shows  a  pressure 
of  12  kg.  to  the  square  centimeter.  The  valve  o  is 
now  closed.  A  is  then  at  once  opened,  and  the  auto- 
clave, after  being  removed  from  the  water,  is  de- 
tached from  the  manometer  at  d. 

It  is  always  possible  that  in  a  new  apparatus  there 
may  be  some  oil  or  other  organic  substance  in  the 
retort  A,  and  since  this  would  cause  an  explosion 
during  the  generation  of  the  oxygen,  it  is  well  to 
first  generate  oxygen  with  a  open.  In  one  experi- 
ment the  author  purposely  added  some  oil  to  the 


424  GAS  ANALYSIS  PART  in 

mixture  of  manganese  dioxide  and  potassium  chlo- 
rate for  the  purpose  of  ascertaining  the  results  of 
such  an  explosion.  It  was  found  that  the  arrange- 
ment of  the  apparatus  above  described  offered  com- 
plete protection  to  the  operator.  The  manometer 
was  broken,  but  no  other  damage  resulted. 

It  is  self-evident  that  the  mixture  of  manganese 
dioxide  and  potassium  chlorate  must  be  completely 
free  from  organic  substance,  sulphur,  etc. 

The  oxygen  is  given  off  at  temperatures  between 
210°  and  390°  ;  the  retort  A  is  scarcely  attacked  at 
this  temperature,  and  it  can  be  used  for  hundreds  of 
experiments.  The  retort  is  thoroughly  cleaned  after 
every  determination  by  boiling  it  out  with  water. 
Direct  experiments  showed  that  about  1  ccm.  of 
chlorine  is  given  off  with  every  1000  ccm.  of  oxy- 
gen. The  chlorine  is  completely  removed  by  insert- 
ing into  the  tube  a  close  roll  of  brass  wire-gauze. 
The  oxygen,  which  then  passes  over  into  the  auto- 
clave <?,  is  chemically  pure.  The  wire-gauze  is  re- 
newed after  each  experiment. 

By  the  foregoing  operation  the  autoclave  is  filled 
with  oxygen  which  is  almost  absolutely  pure. 

When  the  autoclave  has  been  filled  with  oxygen 
by  either  of  the  foregoing  methods,  it  is  carefully 
freed  from  adhering  water  by  wiping  it  with  filter 
paper,  and  is  then  placed  in  the  calorimeter  G-  (Fig. 
127),  the  latter  having  first  been  filled  with  1  liter 
of  water. 

The  calorimeter  consists  of  a  metal  vessel  6r  sup- 
plied with  a  cover,  and  hung  in  a  wooden  vessel  H, 
a  space  of  about  2  cm.  existing  between  6r  and  the 
wood.  In  the  calorimeter  is  a  stirrer  N,  and  a  fine 


CHAP,  xii        THE    HEATING   POWER   OF  FUEL 


425 


thermometer  K,  upon  which  hundredths  of  a  degree 
can  be  read.  The  stirrer  consists  of  a  semicircular 
piece  of  sheet-iron,  and  it  can  be  moved  up  and  down 


FIG.  127. 

by  means  of  two  guide  rods  and  a  cord  which  passes 
through  a  hook  above. 

The  apparatus  is  connected  with  a  dip-battery  by 
means  of  the  two  wires  L  and  M,  and  the  mercury 
contacts  g  and  h.  After  the  autoclave  has  been 
placed  in  the  calorimeter  and  everything  made  ready, 
the  apparatus  is  allowed  to  stand  until  the  thermome- 


426  GAS  ANALYSIS  PART  in 

ter  shows  no  difference  in  two  readings  made  five 
minutes  apart.  The  platinum  wire  in  the  coal  is 
then  heated  to  glowing  by  lowering  the  battery 
plates,  and  the  ignition  of  the  coal  is  thus  effected. 
The  water  is  constantly  stirred,  and  the  thermometer 
is  watched  until  the  mercury  begins  to  fall  again. 
The  temperature  at  the  beginning  and  the  highest 
temperature  at  the  end  are  noted. 

The  calorimetric  determination  proper  takes  about 
fifteen  minutes  ;  the  complete  preparation  for  it  can 
easily  be  made  in  an  hour. 

The  heat-capacity  of  the  whole  apparatus  (auto- 
clave and  calorimeter)  is  best  determined  by  the 
combustion  of  charcoal,  cane-sugar,  cellulose,  or 
naphthalene.  Such  an  amount  of  the  substance  is 
taken  as  will  give  off  about  the  same  amount  of  heat 
as  that  produced  by  1  g.  of  average  coal. 

All  errors  arising  from  the  radiation  of  the  ap- 
paratus, the  formation  of  nitric  acid  from  the  nitro- 
gen of  the  air,  etc.,  are  thus  made  self -compensating 
in  the  experiment. 

Suitable  charcoal  is  prepared  by  cutting  out  small 
cylinders  1  g.  in  weight  from  a  piece  of  ordinary 
charcoal,  placing  these  pieces  in  a  fire-clay  crucible, 
covering  them  with  charcoal  powder,  and  heating 
the  crucible  as  high  as  possible  in  a  gas  blast  fur- 
nace or  in  a  crucible  furnace.  If  the  pieces  are 
removed  from  the  crucible  while  still  at  a  tempera- 
ture of  from  200  to  300°,  and  are  at  once  transferred 
to  dry  weighing  tubes  provided  with  tightly  fitting 
ground  glass  stoppers,  the  charcoal  may  then  be 
regarded  as  consisting  of  pure  carbon  exclusive  of 
the  ash.  The  percentage  of  ash  is  easily  ascertained 


CHAP,  xii        THE   HEATING  POWER   OF  FUEL  427 

by  burning  a  few  of  the  pieces  in  a  platinum  crucible. 
The  absolute  heating  power  of  carbon  is  8080  calo- 
ries, of  cane-sugar  is  8866,  of  cellulose  4140,  and  of 
naphthalene  9692.  If  naphthalene  is  used  in  cali- 
brating the  apparatus,  it  is  compressed  into  cylinders 
in  exactly  the  same  manner  as  described  above  for 
coal. 

Since  all  coals  contain  sulphur,  some  sulphur  diox- 
ide and  sulphuric  acid  are  always  formed  in  the  com- 
bustion. Direct  experiment  showed,  however,  that 
an  iron  apparatus  may  nevertheless  be  employed 
even  although  it  exposes  to  the  action  of  the  gases 
large  surfaces  of  iron  that  are  not  covered  with 
enamel,  for  it  has  been  found  that  the  amount  of 
heat  generated  by  the  action  of  these  acids  on  the 
metal  of  the  autoclave  is  so  small  that  it  cannot  be 
measured. 

In  purely  scientific  investigations  where  the  price 
of  the  apparatus  is  of  secondary  importance  and 
where  the  highest  possible  accuracy  is  desired,  it  is 
better  to  use  an  autoclave  that  is  coated  on  the  inside 
with  platinum. 

The  following  examples  serve  as  illustrations  of 
determinations  of  this  kind:  — 

1.   Coal  I.  —  a  mixture  of  brown  coal  and  bituminous  coal. 
Amount  taken,  0.9878  g. 

Initial  temperature  of  the  calorimeter       .     14.19° 
Final  «  "  .     18.78° 

Hence  the  combustion  caused  a  rise  of  temperature 
of  4.59°  in  the  calorimeter,  and  1  g.  of  coal  would 
have  caused  a  rise  of  temperature  of  4.65°. 


428 


GAS  ANALYSIS 


FART  III 


2.  Coal  I.— 0.835  g. 

Initial  temperature  . 

Final  " 

Rise  of         "  . 

"  "  for  1  g. 

3.  Coal  L  — 0.988  g. 

Initial  temperature  . 

Final  " 

Rise  of         "  . 

"  "  for  1  g. 

4.  Coal  II.  — 0.952  g. 

Initial  temperature  . 


Final 
Rise  of 


for  1  g. 


5.  Coal  II.  — 0.992  g. 

Initial  temperature  . 

Final  " 

Rise  of         «  . 

"  "  for  1  g. 

6.  Sugar-coal  —  0.5617  g. 
Coal  L  — 0.1065  g. 

Initial  temperature  . 
Final  " 


13.82° 

17.70° 

3.88° 

4.65° 


13.68° 

18.29° 

4.61° 

4.66° 


14.62° 

18.98° 

4.36° 

4.47° 


14.72° 
19.30° 

4.58° 
4.61° 


16.22° 
20.09° 


Rise  of  temperature  of  the  calorimeter  3.87°. 
Since  1  g.  of  Coal  I.  gives  a  rise  of  temperature  of 
4.65°,  0.1065  g.  will  give  a  rise  of  0.49°.  Hence 
the  rise  of  temperature  caused  by  the  0.5617  g.  of 
sugar-coal  is  3.38°,  and  1  g.  of  sugar-coal  would  give 
6.01°  rise  of  temperature. 


CHAP,  xii        THE   HEATING  POWER   OF  FUEL  429 

7.   Sugar-coal  —  0.563  g. 
Coal  L  — 0:174  g. 

Initial  temperature  .        .        .        15.84° 
Final  «  ...        20.02° 

Rise  of          "  ...          4.18° 

Rise  of  temperature  from  0.174  g.  of  Coal  I.  is 
0.81°.  Hence  0.563  g.  of  sugar-coal  causes  a  rise 
of  3.37°,  and  1  g.  of  sugar-coal  would  cause  a  rise 
of  temperature  of  6.00°. 

The  elementary  analysis  of  the  sugar-coal  gave  — 

99.5  per  cent  carbon 
0.1       "         hydrogen 
0.3       "         ash. 

If  the  calorific  value  of  the  sugar-coal  be  taken  as 
99.5  per  cent  that  of  pure  carbon,  the  rise  of  tem- 
perature which  1  g.  of  chemically  pure  carbon  will 
produce  in  the  apparatus  is  found  by  the  proportion — 

99.5  :  100  =  6.01  :z, 
z  =  6.04°. 

Since  the  absolute  heating  power  of  carbon  is 
8080,  the  heating  power  of  Coal  I.  is  given  by  the 
proportion  — 

6.04:  4.65  =  8080  :z, 

x  =  6220  calories. 
Coal  II.  — 

6.04:4.54  =  8080:*, 

x  =  6072  calories. 

In  the  practical  using  of  coal  the  combustion  does 
not  take  place  in  closed  chambers,  —  i.e.  under  con- 
stant volume,  —  but  under  constant  pressure,  so  that, 


430  GAS   ANALYSIS  PART  in 

strictly  speaking,  the  values  thus  found  must  be  some- 
what modified.  If,  however,  we  remember  that  in  the 
combustion  of  pure  carbon  or  pure  cellulose,  in  closed 
chambers,  no  change  of  pressure  takes  place  in  the 
calorimeter,  it  is  seen  that  this  correction  may  be 
wholly  disregarded  in  the  case  of  the  ordinary  moist 
coals. 

For  Coal  I.,  for  example,  the  recalculation  gave  a 
correction  of  6.6  calories,  a  figure  which,  even  in  the 
most  accurate  scientific  researches,  falls  wholly  within 
the  limits  of  the  unavoidable  errors ;  in  fact,  the  latest 
determinations  by  Berthelot  have  given  the  absolute 
heating  power  of  amorphous  carbon  not  as  8080,  as 
usually  taken,  but  as  8137.4  calories. 

In  determining  the  heating  power  of  coals  with 
this  method,  the  water  formed  in  the  combustion, 
together  with  the  moisture  present  as  water  in  the 
coal,  escapes  in  a  gaseous  condition  with  the  products 
of  combustion.  The  values  obtained  by  the  method 
are  not,  therefore,  directly  comparable  for  technical 
purposes.  Such  comparable  values,  however,  are  ob- 
tained when  the  heat  of  evaporation  of  the  water 
escaping  in  the  combustion  is  subtracted  from  the 
heating  power  found.  This  result  is  termed  the 
available  heating  power. 

This  available  heating  power  may  be  calculated 
from  the  Dulong  formula  — 

E  =  80.8  C  +  342.3  ^H  -  -V  22.2  S  -  6  W. 

E  is  the  available  heating  power. 
C  is  the  amount  of  carbon  in  the  substance  in  per 
cent. 


CHAP,  xii        THE   HEATING  POWER   OF   FUEL  431 

H  is  the  amount  of  hydrogen  in  the  substance  in  per 

cent. 
O  is  the  amount  of  oxygen  in  the  substance  in  per 

cent. 
S  is  the  amount  of  sulphur  in  the  substance  in  per 

cent. 
W  is  the  total  per  cent  of  water  which  results  from 

combustion. 

Bunte  has  shown  that  the  values  determined  by 
calorimetric  methods  vary  but  slightly  from  the  values 
calculated  from  the  results  of  a  combustion  analysis. 
The  calorimetric  determination  is  greatly  to  be  pre- 
ferred to  the  combustion  analysis  because  it  is  shorter, 
and  because  it  is  easier  to  obtain  correct  results  by 
means  of  it. 

The  available  heating  power  of  the  coal  may  be 
calculated  from  the  result  found  with  the  calorimeter 
by  first  recalculating  this  last  figure  so  that  it  applies 
to  the  coal  containing  mine  moisture,  and  then  sub- 
tracting from  this  last  result  the  value 


n  here  indicating  the  per  cent  of  the  total  water  set 
free  from  the  coal  that  still  contains  the  "mine 
moisture  "  ;  600  is  the  latent  heat  of  evaporation  of 
water. 

For  most  cases  arising  in  practice  it  will  be  suffi- 
cient to  calculate  the  average  amount  of  hydrogen 
contained  by  the  coal  in  question  in  the  ash-free  and 
water-free  condition,  to  then  add  to  that  the  water 
found  on  drying  at  120°  C.  and  the  "  mine  moisture," 


432  GAS  ANALYSIS  PART  in 

and  to  multiply  the  sum  of  these  three  percentage 
values  by  6  and  then  to  subtract  this  amount  from 
the  absolute  heating  power. 

If  an  analysis  of  the  coal  has  not  been  made,  the 
following  average  values  for  the  hydrogen  present 
may  be  used  :  — 

Bohemian  and  similar  brown  coals      .        6.0  per  cent 

Bituminous  coal 5.5     "" 

Anthracite  coal 4.0     "" 

More  exact  figures  are  obtained  by  directly  deter- 
mining the  amount  of  water  formed  in  the  combus- 
tion. This  can  be  done  by  weighing  the  autoclave 
before  filling  it  with  oxygen  and  weighing  it  again 
after  combustion  has  taken  place  and  the  gaseous 
products  of  combustion  have  been  removed,  and  de- 
termining by  titration  the  sulphuric  acid  and  nitric 
acid  which  have  been  formed  in  the  combustion. 
The  increase  of  weight  of  the  autoclave  after  sub- 
traction of  the  weight  of  the  ash  and  of  the  anhydrides 
of  sulphuric  and  nitric  acids  gives  the  amount  of 
water  which  has  been  formed. 

It  is  better,  however,  to  make  a  direct  determina- 
tion of  the  water  by  means  of  combustion  analysis, 
as  proposed  by  F.  Fischer.  This  is  done  by  placing 
from  0.2  to  0.3  g.  of  coal  in  a  boat  in  a  combustion 
tube  which  contains  a  layer  about  40  cm.  long  of 
granular  copper  oxide,  and  then  burning  the  coal  in 
a  current  of  oxygen.  The  water  which  is  set  free 
is  absorbed  in  a  calcium  chloride  tube  and  weighed. 
In  making  the  analysis  it  is  advisable  to  heat  about 
15  cm.  of  the  copper  oxide  which  lies  next  to  the 
calcium  chloride  tube  not  to  glowing,  but  only  to 


CHAP,  xii       THE   HEATING  POWER  OF  FUEL  433 

from  200  to  300°  C.,  and  to  thus  avoid  the  passage 
into  the  calcium  chloride  of  any  sulphuric  acid  which 
is  produced  by  the  combustion  of  the  sulphur  in  the 
coal.  The  total  amount  of  sulphur  will  be  retained 
by  the  slightly  heated  copper  oxide,  while  all  of  the 
water  escapes.  A  small  wash-bottle  containing  con- 
centrated sulphuric  acid  is  placed  behind  the  calcium 
chloride  tube  to  enable  the  operator  to  judge  of  the 
speed  of  escape  of  the  gases  formed  in  the  combustion. 

As  an  illustration  of  the  method  of  calculation 
of  the  available  heating  power  from  the  analytical 
results,  the  following  example  is  given :  — 

A  very  good  sample  of  brown  coal  was  analysed. 
The  coal  had  7  per  cent  of  "  mine  moisture."  The 
air-dried  coal  contained  19.5  per  cent  of  hygroscopic 
water  when  dried  at  120°,  and  3.8  per  cent  of  ash. 
Its  absolute  heating  power  was  5818  calories.  The 
coal  contained  100  -  (19.5  +  3.8)  =  76.7  per  cent  of 
coal  substance.  If  we  assume  that  the  coal  sub- 
stance of  a  first-class  brown  coal  contains  5.8  per 
cent  of  hydrogen,  then  the  air-dried  coal  contained 

rr£»    rr  r    o 

-  =  4.45  per  cent  of  hydrogen,  from  which, 
100 

in  the  combustion,  would  result  4.45  x  9  =  40.05 
per  cent  water.  19.5  per  cent  of  hygroscopic  water 
is,  however,  already  present  in  the  coal,  therefore  the 
combustion  gases  will  contain  40.05  +  19.5  =  59.5 
per  cent  of  water,  which  has  6  x  59.5  =  357  calories 
of  latent  heat  of  evaporation.  The  air-dried  coal 
therefore  has  an  available  heating  power  of  5818 
—  357  =  5461  calories.  Since,  however,  the  original 
coal  contained  7  per  cent  of  "mine  moisture,"  the 
available  heating  power  of  the  residual  93  per  cent 
2r 


434  GAS  ANALYSIS  PART  in 

of  air-dried  coal  5461 *  93  =  5078.7  calories.     To 

ascertain  the  available  heating  power  of  the  coal 
containing  "mine  moisture,"  the  latent  heat  of 
evaporation  of  this  "  mine  moisture,"  7  x  6  =  42 
calories,  must  be  subtracted  from  the  result  just 
obtained.  The  available  heating  power  of  the  coal 
under  examination  is  therefore  5078.7  —  42  =  5036.7 
calories. 


CHAPTER  XIII 

THE  DETERMINATION  OF  THE  HEATING  POWER 
OF  GASES 

THE  determination  of  the  heating  power  of  gases 
can  be  carried  out  satisfactorily  in  the  gas  calorim- 
eter devised  by  Junker,  provided  the  operator  has 
at  his  disposal  a  large  volume  of  gas  which  is  stored 
in  a  gasometer  and  is  therefore  not  changing  in 
composition  during  the  analysis.  With  the  Junker 
apparatus,  however,  it  is  not  possible  to  determine 
the  heating  power  of  such  small  volumes  of  gas  as 
2  or  3  liters,  nor  does  it  enable  the  operator  to  follow 
the  frequent  changes  that  occur  in  the  composition 
of  a  gas  mixture  that  is  being  evolved  from  a  gas 
producer. 

The  incandescent  system  of  gas  lighting  which  has 
recently  been  so  widely  introduced,  depends  for  its 
efficiency  upon  the  heating  power  of  the  gas,  and  not 
upon  its  luminosity.  There  is  but  little  doubt,  there- 
fore, that  the  future  trend  of  gas  production  will  be 
along  the  lines  of  such  products  as  water  gas  or  pro- 
ducer gas,  and  that  the  chief  problem  of  the  manu- 
facture will  be  to  make  a  cheap  gas  of  high  heating 
power.  The  manufacture  of  gas  in  retorts,  so  far  as 
illuminating  gas  is  concerned,  will  also  probably  be 
replaced  in  part  by  the  manufacture  in  generators. 
This  change  will  make  necessary  a  much  more  elab- 

435 


436  GAS  ANALYSIS  PART  m 

orate  chemical  control,  if  the  product  is  to  be  fairly 
constant  in  composition,  than  has  been  customary  in 
gas  works  up  to  the  present  time.  It  is,  therefore, 
highly  desirable  that  the  chemist  possess  a  rapid 
method  for  determining  the  heating  power  of  gases. 

In  connection  with  another  series  of  investigations 
the  author  has  devised  a  calorimetric  method  which 
has  proven  to  be  very  satisfactory.  The  arrange- 
ment of  the  apparatus  is  shown  in  Fig.  128. 

It  consists  essentially  of  a  burner  A,  so  constructed 
as  to  be  supplied  on  the  one  side  with  oxygen  and 
on  the  other  with  the  gas  under  examination.  It 
is  thus  possible  to  reduce  the  total  amount  of  the 
products  of  combustion  to  such  an  extent  as  to  make 
it  possible  to  completely  cool  them  in  the  copper  tube 
B  of  a  length  of  only  18  cm.  and  a  width  of  3.3  cm. 
The  upper  end  of  the  copper  tube  is  closed,  and  the 
tube  itself  is  firmly  fastened  to  a  tripod  support.  A 
glass  tube  E,  34  cm.  long  and  5  to  6  cm.  wide,  is 
placed  over  B,  and  is  held  in  position  by  means  of  a 
large  rubber  stopper  d.  During  the  combustion  the 
water  in  E  is  vigorously  stirred  by  means  of  a  simple 
stirrer  F.  The  temperature  before  and  after  the 
experiment  is  measured  with  an  accuracy  of  about 
0.02°  with  a  delicate  thermometer  G-  graduated  in 
tenths  of  a  degree.  The  gas  under  examination  is 
stored  in  a  small  flat  reservoir  H,  which  is  of  sheet 
zinc,  and  is  closed  above  and  below  by  the  brass 
stopcocks  k  and  i. 

The  gas  is  ignited  by  means  of  a  very  small  hydro- 
gen flame,  the  hydrogen  being  supplied  by  the  gas 
generator  L. 

It  is  essential  that  equal  quantities  of  hydrogen 


CHAP,  xin      THE   HEATING  POWER   OF    GASES 


437 


and  oxygen  be  used  in  the  different  determinations. 
The  supply  of  these  gases  through  the  two  fine  capil- 
lary tubes  m  and  n  is  therefore  regulated  by  opening 

C 


the  stopcocks  of  the  hydrogen  generator  L  and  the 
oxygen  holder  0  to  such  an  extent  that  bubbles  of 
gas  will  just  fail  to  escape  from  the  open  ends  of  the 
glass  tubes  dipping  down  in  the  cylinders  p  and  q. 
In  this  way  it  is  possible  to  cause  these  gases  to  pass 


438 


GAS  ANALYSIS 


PART  III 


through  openings  of  the  same  size  under  very  nearly 
the  same  pressure. 

The  arrangement  of  the  burner  A  is  shown  in  de- 
tail in  Fig.  129.  A  wide  brass  tube  h  is  fastened  to 
an  iron  base  g.  In  the  side  of  h  there  is  a  small  tube 
c  for  the  introduction  of  the  oxygen.  To  the  upper 
end  of  the  large  tube  h  is  fastened  a  porcelain  tube  d 
which  serves  to  prevent  loss  of  heat  by  conduction 
downward  through  the  metal.  Inside 
of  the  tube  h  are  the  tube  a  through 
which  is  introduced  the  gas  to  be 
burned  and  a  second  very  small  cop- 
per tube  b  for  the  introduction  of  the 
hydrogen.  Both  of  these  inner  tubes 
terminate  in  small  porcelain  tubes. 

To  ascertain  the  heating  power  of 
a  gas,  transfer  it  to  the  reservoir  If 
in  such  a  manner  that  it  will  have 
a  slightly  greater  pressure  than  the 
external  atmosphere.  After  reading 
the  temperature  and  the  height  of  the 
barometer,  open  the  stopcock  k  for  an 
instant  to  bring  the  gas  to  atmospheric  pressure. 
Then  join  the  reservoir  H  to  a  glass  Tr,  close  the 
lower  end  of  r  at  u  with  a  piece  of  rubber  tubing  and 
a  pinchcock,  and  cdnnect  the  side  arm  of  r  with  the 
bottle  Q  by  means  of  a  piece  of  rubber  tubing.  In 
one  of  the  necks  of  Q  the  thermometer  s  is  inserted 
air-tight.  With  the  aid  of  the  glass  tube  t  the 
water  can  be  caused  to  flow  from  Q  at  a  constant 
pressure.  By  opening  the  pinchcock  at  u  for  a  mo- 
ment the  rubber  tube  from  Q  can  be  entirely  filled 
with  water. 


FIG.  129. 


CHAP,  xiii      THE    HEATING   POWER  OF   GASES  439 

Fill  the  calorimeter  E  with  500  ccm.  of  water  and 
after  stirring  it  thoroughly  with  the  stirrer  F  meas- 
ure the  temperature  as  accurately  as  possible  with  the 
thermometer  6r.  The  burner  is,  of  course,  not  yet 
placed  in  position  under  B.  When  the  temperature 
of  the  water  in  E  has  been  ascertained,  a  minute  hy- 
drogen flame  is  lighted  in  the  burner,  and  a  current 
of  oxygen  is  then  turned  on.  The  rapidity  of  the 
oxygen  supply  must  be  determined  once  and  for  all  by 
a  few  preliminary  experiments.  The  entrance  of  the 
oxygen  must  be  so  rapid  that  during  the  combustion 
of  the  gas  a  glowing  splinter  will  at  once  burst  into 
flame  when  brought  to  the  mouth  of  the  copper  tube 
B.  Now  place  the  calorimeter  over  the  burner,  open 
the  stopcocks  k  and  i  of  the  reservoir  H,  and  after  a 
few  seconds  shut  off  the  stream  of  hydrogen.  The 
ignition  of  the  gas  from  H  is  usually  accompanied  by 
a  faint  buzzing  sound.  If  care  is  taken  that  the  hy- 
drogen flame  burns  approximately  the  same  length 
of  time  in  the  calorimeter  in  all  experiments,  very 
uniform  results  are  obtained.  When  the  combustion 
has  once  been  started,  the  water  in  the  calorimeter  is 
constantly  stirred  to  keep  its  temperature  uniform 
throughout. 

Gas  bubbles  will  be  seen  rising  from  the  lower  end 
of  t  in  the  bottle  Q  as  long  as  water  flows  from  the 
bottle  to  the  reservoir  H.  The  end  of  the  experiment 
is  indicated  by  the  appearance  of  water  at  v  in  the 
glass  tube  which  connects  the  reservoir  with  the 
burner.  The  temperature  of  the  water  in  E  is  at 
once  read  and  then  the  water  is  stirred  until  the 
thermometer  begins  to  sink.  The  thermometer  usu- 
ally rises  a  little  after  the  combustion  is  finished, 


440 


GAS   ANALYSIS 


since  the  equalization  of  the  heat  in  the  calorimeter 
takes  place  only  slowly. 

The  calibration  of  the  apparatus  is  effected  by  the 
combustion  of  hydrogen.  The  gas  reservoir  is  filled 
with  hydrogen  in  the  manner  above  described  and 
this  gas  is  then  burned.  The  rise  in  temperature  of 
the  water  thus  obtained  as  compared  with  the  rise  in 
temperature  resulting  from  the  combustion  of  another 
gas  gives  us  the  means  of  calculating  the  heating 
power  of  the  latter. 

A  series  of  such  determinations  follows :  — 
Contents  of  gas  reservoir  H  2388  g.  at  18. 3°  C. 
The  small   hydrogen   igniting  flame  burned  thirty 
seconds  in  each  case. 


Initial 

Final 

Num- 
ber of 
Experi- 
ment 

mom- 
eter 

* 

Barom- 
eter 
mm. 

Temperature 
of  Thermom- 
eter G  in 
Calorimeter 

Temperature 
of  Thermom- 
eter G  in 
Calorimeter 

Rise  of 
Temperature 
in 
Calorimeter 

77*       of1 

E.    °C. 

1 

6.10 

755.2 

6.50 

17.40 

10.90 

2 

6.15 

755.2 

6.60 

17.40 

10.80 

3 

6.25 

755.2 

6.80 

17.65 

10.85 

4 

6.30 

755.2 

7.00 

17.84 

10.84 

5 

7.70 

734.0 

8.20 

18.68 

10.48 

6 

8.50 

735.0 

8.84 

19.36 

10.52 

The  first  four  determinations  were  made  on  the 
15th  of  February,  1900 ;  the  last  two  on  the  21st  of 
February,  1900.  From  the  first  four  determinations 
there  is  obtained  an  average  rise  of  temperature  of 
10.847°  with  hydrogen  at  a  temperature  of  6.1°  and 
under  a  barometric  pressure  of  755.2  mm.  The  last 
two  determinations  give  for  the  same  temperature 


CHAP,  xin      THE   HEATING  POWER  OF  GASES  441 

and  pressure  an  average  value  of  10.83°.  The  con- 
tents of  the  gas  reservoir  in  hydrogen  at  6.1°  C.  and 
755.2  mm.  pressure  therefore  gives  an  average  rise  of 
temperature  of  10. 838°  C.  For  the  sake  of  illustra- 
tion the  following  details  concerning  the  determina- 
tion of  the  heating  power  of  a  sample  of  producer 
gas  are  given. 

Thermometers 12.9° 

Barometer         ......       753.2  mm. 

Reading  on  the  thermometer  6r  in  the  calorime- 
ter :  — 

Initial  temperature 9.82°  C. 

Final  temperature 14.03°  C. 

Rise  of  temperature  in  calorimeter          .          4.21°  C. 

Duration  of  ignition  flame       ...  30  seconds. 

Since  the  tension  of  aqueous  vapour  at  6.1°  is  7  mm. 
and  at  12.9°  is  11.1  mm.,  4.1  mm.  must  be  subtracted 
from  753.2  mm.  in  making  the  calculation.  The  rise 
of  temperature  which  the  gas  under  examination 
would  have  given  if  it  had  been  brought  into  the 
reservoir  at  a  temperature  of  6.1°  and  a  pressure 
755.2mm.  is  found  by  the  equation:  — 

749.1  :  755.2  =      4.21  :  as, 
z  =  4.35°C. 

If  the  absolute  heating  power  of  hydrogen  given  by 
Favre  and  Silbermann,  viz.,  34462  calories,  is  used, 
then  the  absolute  heating  power  of  a  liter  of  hydro- 
gen is  3087  calories,  since  1  liter  of  this  gas  at  0°  and 
760  mm.  pressure  weighs  0.089582  g.  The  heating 
power  of  the  gas  under  examination  is  then  calculated 
according  to  the  following  proportion :  — 


442  GAS  ANALYSIS  PART  in 

10.38:  4.35  =  3087  :  x, 

x  =  1239  calories. 

If  the  gas  reservoir  is  fitted  with  a  correction  tube 
(see  p.  61),  correction  for  variation  in  pressure  may 
be  avoided. 

The  great  advantage  of  the  combustion  of  gases 
with  oxygen  lies  in  the  fact  that  even  the  slight  heat- 
ing power  of  gas  mixtures  which  burn  only  with  dif- 
ficulty can  be  determined. 

The  Flame  Calorimeter 

In  controlling  the  working  of  an  industrial  process 
we  may  use  an  empirically  graduated  instrument  that 
will  give  the  operator  an  approximate 
value  of  the  heating  power  of  the  gas  from 
the  height  of  the  flame  which  the  gas  pro- 
duces when  burning.  The  flame  becomes 
greater  as  the  heating  power  of  the  gas 
increases,  the  reason  for  this  being  that  a 
gas  of  high  heating  power  naturally  needs 
more  oxygen  for  its  combustion,  and  con- 
sequently produces  a  longer  flame  than 
does  a  gas  of  lower  heating  power.  The 
heat  necessary  to  decompose  different 
gases  is  not  constant,  and  therefore  meas- 
urements  made  in  this  manner  are  not 
very  accurate. 

The  arrangement  shown  in  Fig.  130  will  in  many 
cases  suffice  to  determine  with  sufficient  accuracy  the 
heating  value  of  a  gas  mixture.  A  burner  c  with  a 
single  opening  is  placed  upon  a  simple  stand  D.  The 
burner  is  surrounded  by  a  glass  cylinder  provided 


CHAP,  xin      THE   HEATING  POWER   OF  GASES  443 

with  a  scale.  The  pressure  under  which  the  gas 
enters  may  be  read  off  on  the  manometer  B.  The 
instrument  is  graduated  empirically  by  leading  into 
it  gases  of  known  calorimetric  value  under  equal 
pressures,  burning  them,  and  noting  the  height  of 
the  flame  in  each. instance.  To  determine  the  heat- 
ing value  of  another  gas,  this  is  passed  into  the  in- 
strument at  the  same  pressure  as  was  used  in  the 
calibration  and  burned.  The  height  of  the  flame 
then  gives  directly  its  heating  power. 

Since  the  speed  of  escape  of  a  gas  is  dependent 
upon  its  specific  gravity,  very  light  gases  will  give 
somewhat  too  high  results,  and  heavy  gases  will  give 
values  that  are  too  low.  Changes  in  atmospheric 
pressure  will  also  influence  the  height  of  the  flame. 
Notwithstanding  these  drawbacks  it  is  possible,  with 
the  aid  of  this  instrument,  to  make  measurements 
that  will  be  of  considerable  value  in  controlling  an 
industrial  process ;  moreover,  such  measurements  can 
be  made  in  a  few  seconds. 


CHAPTER  XIV 

THE  DETERMINATION  OF    SULPHUR  IN  COAL  AND 
ORGANIC  SUBSTANCES 

THE  sulphur  in  organic  substances  may  be  deter- 
mined by  the  method  of  Berthelot,  the  compound 
being  burned  in  an  autoclave,  and  the  resulting  sul- 
phuric acid  being  then  determined  gravimetrically  or 
volumetrically. 

If  no  autoclave  is  at  the  chemist's  disposal,  the 
combustion  may  be  carried  out  in  an  ordinary  glass 
bottle  in  the  manner  described  below. 

The  substance  under  examination  is  pressed  into 
a  small  cylinder  in  exactly  the  same  manner  as  de- 
scribed for  coal  in  the  preceding  chapter,  a  piece  of 
thread  being  here  also  pressed  into  the  substance. 

If  the  substance  is  in  liquid  form,  it  may  be  dropped 
upon  an  absorption  cube  of  cellulose  through  which 
a  piece  of  thread  has  been  drawn  with  a  needle. 
These  little  blocks  of  cellulose  may  be  obtained  from 
Schleicher  and  Schull  of  Diiren,  Germany. 

The  combustion  is  carried  out  in  a  common  glass 
bottle  of  about  10  liters  capacity,  Fig.  131.  Into 
the  neck  of  the  bottle  is  inserted  a  three-hole  rubber 
stopper.  Through  one  opening  of  the  stopper  passes 
a  tube  with  a  glass  stopcock,  the  tube  being  widened 
above  the  stopcock  into  a  cylinder  containing  about 
50  com.  Through  the  other  two  openings  of  the 

444 


CHAP,  xiv     SULPHUR   IN  ORGANIC   SUBSTANCES 


445 


b! 


stopper  are  inserted  short  glass  tubes  into  which  are 
fused  two  long  platinum  wires  of  about  0.6  mm. 
diameter.  To  the  lower  end  of  one  of  these  wires  is 
fastened  a  small  platinum  basket  made  by  folding 
together  a  piece  of  platinum  wire-gauze.  This 
basket  hangs  about  25  mm.  above  the  bottom  of  the 
bottle.  The  two  wires  are  connected  at  c  by  a  very 
fine  platinum  wire. 

The  glass  tubes  b  and  m  are  partly  filled  with 
mercury  for  the  purpose  of  easily  connecting  the 
two  platinum  wires  with  the  ter- 
minals of  an  electric  battery. 
When  the  apparatus  is  not  in  use, 
these  two  glass  tubes  are  closed 
with  small  cork  stoppers. 

To  make  a  determination  of 
sulphur  with  this  apparatus,  re- 
move the  rubber  stopper  from 
the  bottle,  place  the  cylinder  of 
the  substance  under  examination 
in  the  platinum  basket,  and  twist 
the  thread  around  the  thin  wire 
c.  Fill  the  bottle  with  distilled 
water,  close  it  with  a  solid  rubber 
stopper,  and  place  it  in  an  in- 
verted position  on  an  iron  tripod 
which  stands  in  a. large  porce-  FIG.  131. 

lain  dish.  Pour  water  into  the 
dish  until  it  rises  just  to  the  neck  of  the  bottle. 
Remove  the  stopper  and  fill  the  flask  with  oxygen 
in  the  customary  manner.  A  cylinder  of  com- 
pressed oxygen  is  very  convenient  for  this  purpose. 
Close  the  bottle  again  with  the  solid  stopper  and 


446  GAS  ANALYSIS  PART  in 

bring  it  into  an  upright  position.  Remove  this 
stopper  and  lower  into  the  bottle  the  other  stopper 
carrying  the  platinum  wires  and  the  substance  to  be 
burned.  Since  oxygen  is  heavier  than  air,  no  ap- 
preciable amount  of  it  escapes  in  this  operation.  A 
slight  excess  of  pressure  is  created  in  the  bottle  by 
the  combustion  and  it  is  therefore  best  to  hold  the 
stopper  in  place  by  means  of  a  wire  ligature.  Now 
connect  the  apparatus  with  the  poles  of  a  dip  battery 
or  other  source  of  current  and  ignite  the  substance 
by  heating  the  small  platinum  wire  to  incandescence. 
If  the  substance  lies  near  the  bottom  of  the  bottle,  the 
combustion  is  effected  without  difficulty,  the  hot  prod- 
ucts of  the  combustion  rising  to  the  upper  part  of  the 
bottle,  and  fresh  oxygen  constantly  flowing  toward 
the  substance.  After  the  combustion  is  complete 
pour  some  cold  water  over  the  bottle  to  cause  the 
pressure  within  the  bottle  to  fall  slightly  below  that 
of  the  external  atmosphere,  and  then  introduce  into 
the  bottle,  through  the  funnel  tube  and  stopcock, 
about  100  com.  of  distilled  water  to  which  has  been 
added  5  ccm.  of  concentrated  hydrochloric  acid  and 
a  very  small  drop  of  pure  bromine. 

Since  the  greater  part  of  the  water  produced  in 
the  combustion  remains  suspended  in  the  bottle  in 
the  form  of  mist,  it  is  well  to  allow  the  bottle  to 
stand  for  fully  an  hour,  or  at  any  rate  until  the  mist 
has  completely  disappeared.  All  parts  of  the  inner 
surface  of  the  bottle  are  then  carefully  rinsed  with 
the  solution  which  has  been  introduced  and  this  is 
poured  into  a  beaker. 

In  determining  the  sulphur  in  coals  which  necessi- 
tate, because  of  the  ash  present,  a  nitration  of  the 


CHAP,  xiv    SULPHUR   IN   ORGANIC   SUBSTANCES  447 

hydrochloric  acid  solution  of  the  sulphuric  acid,  it  is 
best  to  wash  the  bottle,  the  platinum  basket,  and  the 
platinum  wires  with  portions  of  water  of  75  ccm.  each, 
and  to  begin  the  nitration  of  the  first  portion  at  once. 
By  using  these  various  nitrates  for  the  further  rins- 
ing of  other  parts  of  the  apparatus,  it  is  possible  to 
completely  remove  all  of  the  sulphuric  acid  and  yet 
keep  the  total  volume  of  liquid  down  to  500  ccm. 

The  total  liquid  is  now  heated  to  boiling  and  pre- 
cipitated in  the  usual  way  with  barium  chloride, 
the  barium  sulphate  being  then  filtered  off,  ignited, 
purified,  and  weighed. 

The  following  analytical  results  illustrate  the  degree 
of  accuracy  which  can  be  obtained  by  this  method. 

The  analysis  of  milk  casein  (prepared  by  dissolving 
it  three  times  and  precipitating  it  three  times  with 
acetic  acid  in  the  cold)  gave  upon  combustion  in  the 
bottle  two  exactly  agreeing  results  of  0.74  per  cent 
sulphur. 

According  to  the  determinations  of  Hammarsten  the 
sulphur  contents  lie  between  0.74  and  0.79  per  cent. 

The  determination  of  sulphur  in  different  samples 
of  brown  coal  gave :  — 

1.  By  combustion  in  the  bottle  0.74  per  cent, 

by  Eschke's  method         .         .         .         .0.66 

2.  By  combustion  in  the  bottle  0.86  per  cent, 

by  Eschke's  method         .         .         .         .0.85 

3.  By  combustion  in  the  bottle  0.95  per  cent, 

by  Eschke's  method         .         .         .         .0.91 

These  results  show  that  the  variations  lie  com- 
pletely within  the  limits  of  experimental  error,  and 
that  the  method  is  thoroughly  satisfactory  both  as  to 
simplicity,  rapidity,  and  accuracy. 


CHAPTER   XV 

THE  RECOGNITION  AND  DETERMINATION  OF  METH- 
ANE BY  MEANS  OF  THE  FLAME  TEST 

ON  account  of  the  frightful  disasters  which  result 
almost  every  year  from  the  explosion  of  mine  gases, 
it  is  of  the  highest  importance  to  be  able  to  detect 
with  absolute  certainty  the  presence  of  methane  in 
the  air  of  the  mine. 

Its  detection  is  possible  with  the  aid  of  the  com- 
bustion analysis.  Samples  of  the  air  of  the  mine  are 
collected  for  this  purpose  in  small  glass  tubes  pro- 
vided with  stopcocks  and  containing  about  100  ccm. 
(see  p.  8,  Fig.  6).  The  carbon  dioxide  in  these 
samples  is  first  absorbed  and  the  gas  is  then  burned 
by  one  of  the  methods  described  on  pp.  130  to  143. 
The  volume  of  carbon  dioxide  formed  in  the  com- 
bustion is  equal  to  the  volume  of  methane  which  is 
present  in  the  sample,  for  methane  is  almost  the 
only  combustible  gas  which  occurs  in  the  air  of  coal 
mines.  If  a  burette  filled  with  mercury  and  pro- 
vided with  temperature  and  pressure  correction  is 
used  in  making  the  analysis,  it  is  possible  to  detect 
with  certainty  0.2  per  cent  of  methane. 

Following  the  suggestion  of  Davy,  it  has  long 
been  the  custom  to  detect  the  presence  of  methane 
by  observing  the  aureole  which  the  presence  of  this 
gas  causes  to  appear  around  the  flame  of  an  oil  lamp. 

448 


CHAP,  xv          DETERMINATION   OF   METHANE  449 

Mallard,  Le  Chatelier,  and  Clowes  have  increased 
the  delicacy  of  the  flame  test  to  about  0.25  per  cent 
by  the  use  of  a  hydrogen  flame.  Pieler  has  obtained 
the  same  result  with  a  large  lamp  fed  with  alcohol. 

Neither  of  these  lamps,  however,  is  suited  for 
general  use,  for  they  are  either  too  complex  or  too 
expensive. 

The  author  has  endeavoured  to  so  modify  the  mine 
safety  lamp  of  Friemann  and  Wolf  as  to  adapt  it  for 
the  simultaneous  detection  of  methane. 

Long  experimentation  has  shown  that  for  this  pur- 
pose the  hydrogen  flame  is  unquestionably  superior 
to  all  other  flames.  There  is,  therefore,  attached  to 
the  lower  part  of  the  lamp  a  simple  apparatus  for 
the  generation  of  hydrogen,  with  the  aid  of  which  a 
small  hydrogen  flame  can  at  any  moment  be  started 
in  the  interior  of  the  lamp.  The  hydrogen  genera- 
tor is  of  sufficient  capacity  to  maintain  a  flame  for 
from  two  to  three  hours. 

The  lamp  (Fig.  132)  consists  of  a  benzine  burner 
-4.,  a  glass  cylinder  j?,  a  chimney  0  made  of  fine- 
mesh  gauze,  the  hydrogen  generator  D,  and  the  acid 
reservoir  E. 

The  reservoir  of  the  benzine  burner  is  filled  with 
cotton,  and  the  wick  passes  up  into  the  tube  a. 
This  wick  can  be  run  up  and  down  by  means  of  a 
small  screw,  and  if  the  benzine  flame  goes  out  it  can 
be  lighted  again,  without  opening  the  lamp,  by  the 
ignitor  5,  which  contains  bits  of  phosphorus. 

The  hydrogen  generator  D  is  made  entirely  of 
lead,  and  is  attached  to  the  lower  part  of  the  ben- 
zine lamp  by  means  of  screws.  Short  pieces  of 
rubber  tubing  serve  to  connect  D  on  the  one  hand 


450 


GAS   ANALYSIS 


with  the  large  reservoir  E,  and  on  the  other  with 
the  hydrogen  burner  c.  A  perforated  lead  plate  d 
serves  to  support  the  granulated  zinc  from  which 
hydrogen  is  evolved  by  bringing  it  into  contact  with 

a  dilute  solution  of  sul- 
phuric acid  (one  part  of 
concentrated  acid  to  four 
parts  by  volume  of  water). 
The  flow  of  acid  from  the 
reservoir  is  regulated  by  a 
screw  pinchcock  g,  and  the 
size  of  the  hydrogen  flame 
by  the  other  screw  pinch- 
cock  e.  The  amount  of 
methane  in  the  air  of  the 
mine  is  read  off  directly 
on  the  scale  /,  which  is 
marked  upon  the  side  of 
the  glass  cylinder  B.  The 
evolved  hydrogen  carries 
with  it  a  fine  spray  of  the 
acid.  To  prevent  this  acid 
from  entering  the  burner 
there  is  introduced,  be- 
tween %  and  the  burner  c, 
a  U-shaped  glass  tube  h. 
The  upper  part  of  this 
tube  is  loosely  filled  with 
cotton,  h  hangs  on  the  outside  of  the  lamp,  and  it 
is,  therefore,  easy  to  renew  the  cotton  if  it  should 
become  so  moist  as  to  hinder  the  passage  of  the 
hydrogen.  The  opening  of  the  hydrogen  burner  is 
so  small  as  to  render  it  impossible  for  the  flame  to 


FIG.  132. 


CHAP,  xv          DETERMINATION  OP  METHANE  451 

strike  back  into  the  hydrogen  generator,  even  when 
this  generator  is  filled  with  oxyhydrogen  gas. 

Before  going  into  the  mine  the  generator  is 
freshly  filled  with  zinc  and  acid,  the  pinchcock  g  is 
closed,  and  the  evolution  of  the  hydrogen  is  started 
only  when  the  examination  of  the  air  in  the  mine  is 
desired.  In  testing  for  the  presence  of  methane, 
both  of  the  pinchcocks  g  and  e  are  opened,  and  when 
the  hydrogen  flame  has  begun  to  burn  the  benzine 
flame  is  turned  down  very  low.  It  is  easy  to  dimin- 
ish the  size  of  the  benzine  flame  to  such  an  extent  as 
to  completely  prevent  any  disturbance  by  it  of  the 
observations.  The  hydrogen  flame  is  then  brought 
to  normal  height  by  means  of  the  pinchcock,  and  the 
amount  of  methane  present  is  read  off  from  the 
length  of  the  aureole.  When  the  examination  is 
ended,  the  benzine  flame  is  again  turned  up  high 
and  the  pinchcock  e  is  closed.  The  pressure  of  the 
hydrogen  gas  then  drives  the  acid  back  into  the  res- 
ervoir E.  Any  excess  of  hydrogen  can  escape 
through  the  capillary  tube  m  in  the  rubber  stopper  n. 


CHAPTER   XVI 
THE  GAS  LANTERN 

AN    APPARATUS    FOR    CONTROLLING    GAS    PRO- 
CESSES, AND    ESPECIALLY    FOR    THE    INSPECTION 

OF  HEATING  PLANTS 

IN  many  cases  the  technical  chemist  is  called  upon 
to  so  conduct  a  gas  process  as  to  cause  it  to  run  uni- 
formly over  a  long  period  of  time.  The  solution  of 
this  problem  will  be  greatly  facilitated  if  there  is 
obtainable  a  simple,  cheap  apparatus  which  will  indi- 
cate at  once  changes  in  the  composition  of  the  gas. 
This  is  especially  true  in  the  handling  of  heating 
plants.  In  commercial  practice,  the  combustion  of 
coal  must  be  carried  on  with  the  aid  of  air,  and  a 
great  loss  of  heat  is  unavoidable  if  the  introduction 
of  an  unnecessary  excess  of  air  is  not  carefully 
avoided.  Such  an  excess  reduces  the  temperature 
of  the  flame,  and  also  carries  off  a  very  considerable 
amount  of  heat  through  the  chimney.  Air  contains 
only  20.92  per  cent  of  oxygen,  and,  therefore,  for 
every  unnecessary  volume  of  oxygen  used  nearly 
four  times  that  volume  of  nitrogen  is  added. 

This  explains  why  the  introduction  of  too  much 
air  causes  such  an  enormous  loss  of  heat.  Every 
boiler  plant  is,  of  course,  provided  with  a  water 
gauge  and  pressure  gauge,  but  one  rarely  finds  any 
arrangement  for  ascertaining  the  composition  of  the 

452 


CHAP,  xvi  THE   GAS   LANTERN  453 

flue  gas,  although  this  is  absolutely  essential  for  eco- 
nomic working.  The  lack  of  such  an  apparatus  is 
doubtless  due  to  the  fact  that  until  very  recently 
there  was  no  cheap  instrument  which  equalled  the 
gauge  in  simplicity,  and  which  at  a  glance  gave  in- 
formation as  to  the  completeness  of  the  combustion 
at  any  moment.  At  the  present  time  a  heating 
plant  is  controlled  either  by  the  use  of  an  apparatus 
for  analysing  the  flue  gases  or  by  the  employment  of 
a  gas  balance.  The  analysis  of  the  gas  takes  several 
minutes,  and  a  gas  balance,  though  it  gives  the 
results  more  quickly,  is  a  very  delicate  and  quite  ex- 
pensive piece  of  apparatus. 

There  is  described  below  an  arrangement  by 
means  of  which  the  condition  of  the  fire  or  of  the 
process  in  which  gases  are  being  evolved  can  be 
judged  with  ease,  this  judgment  being  based  upon 
the  fact  that  a  flame  changes  in  size  as  the  amount 
of  oxygen  in  the  gas  mixture  changes. 

The  various  forms  of  apparatus  proposed  by  Mal- 
lard and  others,  and  described  on  p.  449,  were  de- 
vised for  the  purpose  of  detecting  the  smallest  possible 
quantities  of  methane.  The  apparatus  described  in 
this  chapter  enables  us  to  use  a  flame  for  the  deter- 
mination of  large  amounts  of  the  gases  which  are 
mixed  with  the  air.  It  was  found  upon  experiment 
that  every  flame  at  once  changes  its  form  when  the 
composition  of  the  surrounding  atmosphere  changes. 
If  the  flue  gases  from  the  furnace  be  allowed  to 
escape  around  a  flame,  the  latter  at  first  lengthens, 
later  loses  its  luminosity,  and  finally  is  extinguished 
when  the  amount  of  oxygen  in  the  gas  mixture  falls 
below  12^  per  cent.  The  gases  from  a  properly 


454  GAS   ANALYSIS  PART  in 

stoked  fire  usually  contain  from  12  to  15  per  cent  of 
carbon  dioxide.  It  is  therefore  apparent  that  a 
flame  cannot  burn  in  the  gases  escaping  from  such  a 
fire.  If,  however,  there  can  be  devised  an  arrange- 
ment by  means  of  which  the  flue  gases  from  a  fur- 
nace are  mixed  with  so  much  air  that  even  with  the 
highest  amounts  of  carbon  dioxide  which  the  com- 
bustion can  produce  the  flame  will  not  be  extin- 
guished, the  length  of  the  flame  can  then  be  employed 
to  judge  of  the  amount  of  carbon  dioxide  present  in 
the  flue  gas.  This  same  arrangement  is  possible 
with  other  gas  processes. 

Figure  133  shows  a  simple  apparatus  which  the 
author  has  devised  for  the  above-described  determi- 
nation. 

A  is  a  pipe  which  is  introduced  into  the  chimney 
beyond  the  damper. 

B  is  a  pipe  through  which  the  flue  gases  enter. 

It  is  advisable  to  draw  off  the  flue  gases  at  the 
end  of  the  visible  flame,  and  before  they  have  passed 
through  long  stretches  of  brickwork,  because  the 
wall  is  never  air-tight,  and  large  amounts  of  air  are 
constantly  entering  through  it. 

The  flame  always  carries  along  more  or  less  flue 
dust.  To  render  it  possible  to  clean  out  the  sam- 
pling pipe  from  time  to  time,  the  last  portion  of  it  is 
made  about  4  cm.  wide,  and  is  so  arranged  that  its 
outer  end  can  be  opened  and  the  whole  tube  freed 
from  dust  by  pushing  an  iron  rod  through  it. 

(7  and  E  are  large  T-tubes  which  are  joined  to- 
gether by  the  graduated  glass  tube  D. 

G-  is  a  small  tube  drawn  out  to  a  very  small  open- 
ing at  the  tip.  This  tube  Gr  is  connected  with  the 


CHAP.    XVI 


THE   GAS   LANTERN 


455 


gas  supply  by  the  rubber  tube  L,  and  is  held  in 
place  in  the  lower  end  of  E  by  means  of  the  stopper  m. 
Small  dampers  at  h  and  i  permit  of  the  introduc- 
tion of  any  desired  amount  of  air 


A  very  small  lead  pipe  is  connected  with  E  at  w, 
and  this  tube  is  itself  joined  to  the  draft  measurer  F. 
This  draft  measurer  F  is  constructed  on  the  plan 
suggested  by  Kretz,  and  consists  of  an  upright  cyl- 
inder in  which  the  pipette  P  is  held  in  a  vertical 
position  by  means  of  the  stopper  0.  This  stopper 


456  GAS  ANALYSIS  PART  in 

must  not  fit  air-tight  in  the  neck  of  the  cylinder. 
A  mixture  q  of  a  heavy  paraffin  oil,  containing  just 
enough  carbon  disulphide  to  cause  it  to  sink  in 
water,  is  introduced  into  the  cylinder  until  it  stands 
at  a  height  of  about  4  cm.,  and  this  is  then  covered 
with  a  layer  of  water,  as  shown  in  the  figure.  If 
the  pressure  in  the  pipette  P  diminishes,  the  water 
which  the  pipette  contains  will  rise  slightly,  while 
the  paraffin  oil,  which  closes  the  lower  end  of  the 
pipette,  will  be  drawn  up  through  a  much  greater 
distance,  the  amount  of  rise  depending  upon  the 
ratio  between  the  diameter  of  the  pipette  at  x  and 
the  diameter  of  the  tube  at  y.  The  apparatus  thus 
arranged  is  sufficiently  delicate  to  permit  of  the 
reading  of  the  water  pressure  in  hundredths  of  a 
millimeter. 

In  setting  the  apparatus  in  operation,  the  tube  G- 
is  first  removed,  and  the  gas  entering  it  through  the 
rubber  tube  L  is  ignited  at  the  tip  of  Gr.  Ordinary 
illuminating  gas,  water  gas,  or  hydrogen  may  be 
used  for  this  purpose.  A  candle  or  an  oil  lamp  may 
be  used  in  place  of  a  gas  flame,  but  the  apparatus  is 
then  much  less  sensitive. 

The  dampers  i  and  h  are  opened  wide,  the  flame  is 
introduced  into  the  apparatus,  and  the  gas  is  then 
regulated  so  that  the  flame  stands  at  a  certain  height. 
If  the  draft  measurer  F  does  not  stand  in  equilibrium 
when  the  small  dampers  are  opened,  it  is  brought 
to  this  condition  by  pouring  water  either  into  the 
pipette  P  or  into  the  cylinder  of  F.  After  adjusting 
the  apparatus,  the  dampers  or  draft  openings  of  the 
furnace  are  brought  into  such  a  position  as  to  cause 
the  production  of  the  maximum  amount  of  carbon 


CHAP,  xvi  THE   GAS  LANTERN  457 

dioxide  ;  that  is,  they  are  closed  as  far  as  possible 
without  causing  the  extinction  of  the  fire.  The 
small  damper  i  is  then  closed,  and  the  entrance  of 
air  through  h  is  gradually  shut  off  until  the  flame 
just  goes  out.  This  position  of  h  is  then  noted,  and 
at  the  same  time  a  sample  of  the  gas  is  drawn  out 
through  K  and  analysed. 

The  dampers  i  and  h  are  then  opened  once  more, 
and  the  combustion  in  the  furnace  is  brought  to 
normal  conditions.  The  gas  issuing  from  Gr  is  again 
ignited,  i  is  completely  closed,  and  h  is  closed  nearly 
to  the  mark.  It  is  now  possible  to  directly  observe 
changes  in  the  height  of  the  flame  by  reading  this 
off  on  the  scale  of  the  cylinder  .Z),  the  draft  meas- 
urer being  always  kept  in  equilibrium  by  partially 
opening  and  closing  the  damper  i.  With  the  aid  of 
the  analysis  of  the  samples  of  gas  drawn  off  through 
jfiTit  is  easy  to  ascertain  the  amounts  of  carbon  diox- 
ide which  correspond  to  the  different  heights  of  the 
flame. 

The  use  of  the  apparatus  above  described  is  by  no 
means  limited  to  the  control  of  heating  plants.  On 
the  contrary,  if  made  of  suitable  material,  it  may  be 
employed  in  the  examination  of  the  gases  coming  off 
from  sulphate  furnaces,  chlorine  generators,  sulphur 
burners,  etc.,  since  all  of  these  gases  influence  the 
height  of  a  gas  flame  or  the  flame  of  a  lamp.  The 
apparatus  is  very  simple  and  can  easily  be  con- 
structed. It  possesses  further  the  great  advantage 
of  being  usable  in  a  dark  room.  When  gas  flames 
are  employed,  they  increase  in  length  as  the  non- 
combustible  constituents  of  the  gas  mixture  increase 
in  quantity ;  but  with  candles  and  lamps  exactly  the 


458  GAS  ANALYSIS  PART  in 

opposite  is  true,  for  here  the  flame  will  produce  less 
heat  under  these  conditions,  will  consequently  gasify 
less  combustible  material,  and  the  flame  will  there- 
fore be  smaller. 

Long  experience  in  the  use  of  this  apparatus  in 
the  heating  plant  of  the  Dresden  laboratory  has 
shown  that  gas  flames  are  best  for  this  purpose. 
The  flame  fed  with  hydrogen  is  much  more  sensitive 
than  one  supplied  with  ordinary  illuminating  gas. 


CHAPTER   XVII 

THE  VOLUMETRIC  DETERMINATION  OF  CARBON 
IN  IRON 

IN  connection  with  a  comparative  examination l  of 
the  various  methods  which  have  been  proposed  for 
the  determination  of  carbon  in  iron,  the  author  has 
devised  a  procedure  for  volumetrically  determining 
the  carbon  present. 

When  iron  which  contains  carbon  is  dissolved  in 
acids,  copper  sulphate,  or  a  mixture  of  chromic  or 
sulphuric  acids,  a  part  of  the  carbon  is  always  set 
free  in  the  form  of  hydrocarbons.  The  author  has 
found,  however,  that  if  iron  be  treated  with  chromic 
acid  and  sulphuric  acid  in  the  presence  of  mercury, 
it  is  possible  to  so  conduct  the  process  of  solution 
that  no  trace  of  hydrocarbon  will  form,  the  total 
amount  of  the  carbon,  on  the  contrary,  being  set 
free  in  the  form  of  carbon  dioxide. 

The  method  is  briefly  as  follows:  about  0.5  g. 
of  iron  with  about  2.3  g.  of  metallic  mercury  is 
dissolved  under  diminished  pressure  in  a  mixture  of 
chromic  acid,  sulphuric  acid,  and  water.  The  mix- 
ture of  air,  carbon  dioxide,  and  oxygen — the  last  gas 
being  set  free  when  the  chromic  acid  is  boiled  with 
sulphuric  acid  —  is  then  measured,  and  the  carbon 

1  Verhandlungen  des  Vereins  zur  Beforderung  des  Gewerbe- 
fleisses. 

459 


460  GAS  ANALYSIS  PART  in 

dioxide  is  volumetrically  determined  by  absorption 
with  caustic  potash. 

The  determination  is  carried  out  either  in  the  ap- 
paratus shown  in  Fig.  42,  on  p.  75,  or  that  illus- 
trated in  Fig.  110,  on  p.  380. 

The  solutions  which  are  used  are  prepared  as  fol- 
lows :  — 

1.    Chromic  Acid 

The  manufacturers  of  chromic  acid  are  in  the 
habit  of  covering  with  paraffin  the  glass  stoppers  of 
the  bottles  in  which  this  preparation  is  shipped,  and 
consequently  it  is  always  possible  that  organic  sub- 
stances may  be  present  in  the  acid.  It  is  therefore 
best  for  the  chemist  to  prepare  the  chromic  acid 
himself. 

This  is  done  by  dissolving  300  g.  of  commercial 
potassium  dichromate  in  500  ccm.  of  water  and 
420  ccm.  of  concentrated  sulphuric  acid  with  the  aid 
of  heat.  When  solution  is  complete,  the  liquid  is 
allowed  to  stand  for  twelve  hours,  and  the  clear  solu- 
tion is  then  decanted  from  the  crystals  of  primary 
potassium  sulphate  which  have  separated  in  the 
meantime.  The  crystals  are  washed  with  from  10 
to  12  ccm.  of  water,  and  this  water  is  added  to  the 
solution.  The  solution  is  now  warmed  to  from  80° 
to  90°,  and  150  ccm.  of  concentrated  sulphuric  acid 
is  then  added,  together  with  sufficient  water  to  keep 
in  solution  any  chromic  acid  that  may  have  sepa- 
rated. The  whole  is  now  evaporated  until  a  crys- 
talline crust  forms,  and,  after  standing  for  twelve 
hours,  the  separated  chromic  acid  is  removed  by 
nitration  on  a  platinum  cone  with  the  aid  of  suction. 


CHAP,  xvii    DETERMINATION  OF  CAKBON  IN  IKON        461 

The  mother  liquor  is  again  evaporated  until  a  crust 
appears,  and  is  allowed  to  stand  until  a  second  crys- 
tallisation takes  place.  The  liquid  should  not  be 
too  strongly  heated  during  the  evaporation,  since 
oxygen  might  be  set  free  and  chromic  sulphate  be 
formed.  The  entrance  of  any  dust  must,  of  course, 
be  carefully  avoided. 

The  chromic  acid  thus  prepared  naturally  con- 
tains some  free  sulphuric  acid  and  a  little  primary 
potassium  sulphate.  100  g.  of  it  is  dissolved  in 
300  g.  of  water  and  30  g.  of  sulphuric  acid  of  1.704 
specific  gravity  (see  below). 

The  specific  gravity  of  the  solution  thus  prepared 
should  be  1.2.  If  it  is  above  this  figure  it  contains 
too  much  chromic  acid,  and  may  give  rise  to  an  in- 
convenient evolution  of  oxygen  when  the  iron  is  dis- 
solved. 

2.   Sulphuric  Acid 

The  specific  gravity  of  the  acid  should  be  1.704  at 
16  C.,  corresponding  to  about  78  per  cent  of  H2SO4. 

This  is  prepared  by  mixing  1000  ccm.  of  the 
most  concentrated  sulphuric  acid  (this  need  not  be 
chemically  pure)  with  500  ccm.  of  water  and  10  g. 
Cr03. 

This  mixture  is  heated  to  boiling  in  a  large  flask 
on  a  sand  bath  for  an  hour ;  the  flame  is  then  re- 
moved, and  air  is  blown  through  the  liquid  for  five 
minutes,  with  the  aid  of  a  blast  to  remove  any  car- 
bon dioxide  which  may  have  been  formed.  This 
long  boiling  of  the  acid  will,  of  course,  concentrate 
it  to  an  appreciable  degree.  It  is  brought  back 
afterward  to  the  proper  concentration  by  dilution 


462  GAS   ANALYSIS  PART  in 

with  absolutely  pure  water.     A  variation  of  from  1 
to  2  per  cent  is  without  result  upon  the  analysis. 

MANIPULATION  OF  THE  APPARATUS 

About  0.5  g.  of  the  iron  to  tie  analysed  is  placed 
in  a  weighing  tube  (Fig.  134),  and  the  tube  is  then 
accurately  weighed.  The  contents  is  then 
shaken  into  the  flask  of  the  evolution  appa- 
ratus, shown  in  Fig.  110,  p.  380,  and  the 
weighing  tube  is  then  weighed  again,  the 
difference  between  these  two  weights  giving 
the  amount  of  the  sample  used. 

About  2.3  g.  of  mercury  is  then  intro- 
duced into  the  flask  by  means  of  a  small 
pipette  made  from  a  glass  tube  (Fig. 
135). 

The  apparatus  is  now  connected 
together  in  the  manner  shown  in  Fig. 
110,  and  after  the  measuring  tube 
has  been  completely  filled  with  mer- 
cury, f  is  closed,  and  the  flask  is  ex- 
hausted as  completely  as  is  possible 
by  an  ordinary  water  suction  pump 
FIG  134  Cached  to  k.  To  insure  the  ground- 
glass  joints  of  the  apparatus  being 
air-tight,  a  little  water  is  placed  in  the  bell  ?, 
and  30  ccm.  of  the  chromic  acid  solution  is 
placed  in  m.  The  stopcock  n  is  then  closed, 
and  the  tube  o  is  carefully  raised  to  allow  the 
30  ccm.  of  the  chromic  acid  solution  to  enter  the 
flask.  Water  is  started  through  the  Liebig  con- 
denser, and  the  contents  of  the  flask  is  heated  to  the 


CHAP,  xvn    DETERMINATION  OF  CARBON  IN  IRON        463 

boiling-point  by  means  of  a  very  small  flame.  The 
boiling  proceeds  quietly  because  of  the  diminished 
pressure  prevailing  in  the  flask,  and  is  continued 
for  thirty  minutes.  At  the  expiration  of  this  inter- 
val 120  ccm.  of  sulphuric  acid,  solution  2,  is  intro- 
duced through  the  tube  w,  and  the  contents  of  the 
flask  is  again  boiled  for  thirty  minutes. 

The  pinchcock  f  is  not  opened  until  there  has 
been  developed  in  the  flask  sufficient  carbon  dioxide 
to  overcome  the  diminished  pressure  which  first  pre- 
vailed there,  and  to  thus  prevent  the  entrance  of 
mercury  from  the  burette  into  the  flask.  This  equal- 
isation of  the  pressure  usually  occurs  after  the  addi- 
tion of  the  sulphuric  acid  solution. 

In  the  beginning  of  the  operation  carbon  dioxide 
alone  is  evolved ;  but  as  the  temperature  rises  a  quite 
active  evolution  of  oxygen,  due  to  the  action  of  the 
sulphuric  acid  on  the  chromic  acid,  takes  place 
toward  the  end  of  the  process. 

The  possibility  that  the  apparatus  may  break  at 
any  time,  and  that  serious  injury  to  the  operator 
may  be  caused  by  the  boiling  sulphuric  acid,  should 
always  be  borne  in  mind,  and  the  eyes  should 
always  be  protected  by  goggles. 

After  the  second  boiling  for  thirty  minutes  is  fin- 
ished the  flame  is  removed,  and  the  tube  m  is  filled 
with  distilled  water.  The  tube  o  is  now  very  carefully 
lifted,  and  there  is  allowed  to  enter  the  flask  water 
sufficient  to  drive  all  of  the  gas  over  into  the  meas- 
uring tube.  Great  care  should,  however,  be  taken 
to  avoid  the  entrance  of  any  liquid  into  the  burette. 
If  a  burette  of  the  form  shown  in  Fig.  36,  II,  has 
been  employed,  and  the  gas  which  has  been  evolved 


464  GAS  ANALYSIS  PART  in 

is  not  sufficient  to  fill  it  down  to  the  graduated  por- 
tion, then  air  is  admitted  until  the  mercury  has 
fallen  to  the  graduation.  The  total  volume  of  gas  is 
now  measured. 

To  absorb  the  carbon  dioxide,  the  burette  is  con- 
nected with  a  simple  gas  pipette  for  solid  and  liquid 
reagents,  Fig.  32,  p.  49,  the  pipette  being  filled  with 
a  solution  of  potassium  hydroxide.  The  gas  is 
driven  over  into  the  pipette,  is  drawn  back,  and  is 
again  measured.  The  difference  between  the  two 
measurements  gives  the  volume  of  carbon  dioxide 
which  has  been  evolved. 

Several  experiments  showed  that  a  single  passage 
of  the  gas  mixture  into  the  gas  pipette  sufficed  to 
remove  the  last  trace  of  carbon  dioxide. 

The  iron  used  in  the  analysis  should  not  be  in  too 
large  pieces.  In  the  case  of  steel  or  gray  pig-iron, 
ordinary  borings  may  be  directly  employed.  With 
spiegeleisen  the  pieces  must  be  pulverised  in  a 
heavy  mortar  until  they  will  pass  through  a  sieve  of 
from  400  to  500  meshes  per  square  centimeter. 


ANALYTICAL  RESULTS 

The  following  analyses  will  give  an  idea  of  the  ac- 
curacy of  the  method  :  — 

1.    Crray  Cast-iron 

0.5045  g.  of  iron  from  the  surface  of  a  piece  of 
gray  cast-iron  gave  32.0  ccm.  of  carbon  dioxide,  cor- 
responding to  3.40  per  cent  of  carbon. 

The   gas   residue   which   was   not   absorbable   by 


CHAP,  xvn     DETERMINATION  OF  CARBON  IN  IRON        465 

caustic  potash  was  burned  with  the  addition  of  hy- 
drogen, but  gave  no  trace  of  carbon  dioxide. 

0.4797  g.  of  iron  from  the  inside  of  the  same  piece 
of  gray  cast-iron  gave  28.66  ccm.  of  CO2,  correspond- 
ing to  3.21  per  cent  C. 

0.3889  g.  of  iron  from  the  inside  of  the  same  sam- 
ple gave  23.45  ccm.  CO2,  corresponding  to  3.237  per 
cent  C. 

0.4260  g.  of  iron  from  the  inside  of  the  same  sam- 
ple gave  25.85  ccm.  CO2,  corresponding  to  3.257  per 
cent  C. 

2.    Spiegeleisen 

0.2812  g.  of  spiegeleisen,  pulverised  until  all  of 
the  grains  passed  through  a  sieve  of  from  400  to 
500  meshes  per  square  centimeter,  gave  25.16  ccm. 
CO2,  corresponding  to  4.798  per  cent  C. 

The  gas  residue,  which  was  not  absorbable  by  po- 
tassium hydroxide  when  burned  with  hydrogen, 
gave  0.2  ccm.  carbon  dioxide,  resulting  from  the 
hydrocarbons,  which  had  been  evolved. 

0.338  g.  of  the  same  spiegeleisen  gave  32.37  ccm. 
CO2,  corresponding  to  5.131  per  cent  C. 

The  gas  residue,  which  was  not  absorbable  by  po- 
tassium hydroxide,  was  burned  with  hydrogen,  and 
yielded  0.1  ccm.  carbon  dioxide,  resulting  from  the 
hydrocarbons,  which  had  been  evolved. 

3.    Cast- steel 

0.7932  g.  of  cast  steel  gave  13.73  ccm.  CO2,  cor- 
responding to  0.9282  per  cent  C. 

Upon  passing  the  gas  a  second  time  into  the  caus- 


466  GAS   ANALYSIS  PART  in 

tic  potash  pipette,  a  further  contraction  of  0.1  ccm. 
took  place. 

0.5730  g.  of  the  same  sample  of  cast-steel  gave 
9.82  ccm.  CO2,  corresponding  to  0.919  per  cent  C. 

Upon  passing  the  gas  a  second  time  into  the  caus- 
tic potash  pipette,  a  further  contraction  of  0.1  to  0.2 
ccm.  took  place. 

0.5900  g.  of  the  same  sample  of  cast-steel  gave 
10.42  ccm.  CO2,  corresponding  to  0.947  per  cent  C. 

0.4945  g.  of  the  same  sample  of  cast-steel  gave 
8.719  ccm.  CO2,  corresponding  to  0.9455  per 
cent  C. 

0.58725  g.  of  the  same  sample  of  cast-steel  gave 
10.12  ccm.  CO2,  corresponding  to  0.9240  per  cent  C. 

0.605  g.  of  the  same  sample  of  cast-steel  gave 
10.52  ccm.  CO2,  corresponding  to  0.9326  per  cent  C. 

4.    Ingot  Iron 

0.5292  g.  of  ingot  iron  gave  1.502  ccm.  CO2,  cor- 
responding to  0.1523  per  cent  C. 

The  gas  residue  amounted  to  30.90  ccm.  To  this 
12.7  ccm.  of  hydrogen  was  added,  and  the  mixture 
was  exploded.  The  volume  after  explosion  was  23.3 
ccm.,  and  after  passage  into  the  caustic  potash 
pipette  was  23.2  ccm.,  hence  no  hydrocarbons  had 
evolved. 

It  is  apparent  that  measurement  of  carbon  dioxide 
may  easily  give  lower  results  than  weighing  of  the 
gas.  There  are,  therefore,  added  below  two  analy- 
ses of  ingot  steel,  in  which  a  large  quantity  of  steel 
was  dissolved  exactly  in  the  method  above  described, 
with  the  aid  of  mercury,  chromic  acid,  and  sulphuric 


CHAP,  xvn     DETERMINATION  OF  CARBON  IN  IRON        467 

acid,  but  in  which  the  carbon  dioxide  instead  of 
being  measured  was  weighed. 

2.5155  g.  of  ingot  steel  gave  0.098  g.  CO2,  corre- 
sponding to  1.06  per  cent  C. 

2.5173  g.  of  ingot  steel  gave  0.0928  g.  CO2,  corre- 
sponding to  0.95  per  cent  C. 

Attention  must  be  called  to  the  fact  that  certain 
kinds  of  iron,  as,  for  example,  spiegeleisen,  are  dis- 
solved only  with  difficulty  by  a  mixture  of  chromic 
acid  and  sulphuric  acid.  In  such  a  case  it  is  better 
to  use  the  Berzelius-Wohler  chlorine  method,  for 
this  can  be  employed  without  carefully  pulverising 
the  sample. 

It  is,  of  course,  possible  to  use  in  this  method  any 
suitable  measuring  apparatus  instead  of  the  burette 
described ;  for  example,  an  ordinary  gas  burette  or  a 
nitrometer,  if  the  operator  wishes  to  avoid  the  ex- 
pense of  a  new  apparatus  and  has  any  measuring 
instrument  at  hand.  It  is  also  always  possible  to 
determine  the  carbon  dioxide  by  weighing,  and  to 
thus  completely  dispense  with  the  measuring  appa- 
ratus ;  but  in  this  case  it  is  necessary  to  use  large 
amounts  of  substance,  for  the  weighing  of  the  gas  in 
as  large  vessels  as  the  ordinary  potash  pipettes  is  by 
no  means  as  delicate  and  accurate  a  procedure  as  the 
measurement  of  the  volume  of  the  gas. 


CHAPTER  XVIII 

THE  VOLUMETRIC  DETERMINATION  OF  THE 
STRENGTH  OF  "CHLORIDE  OF  LIME,"  PYRO- 
LUSITE,  POTASSIUM  PERMANGANATE  AND 
HYDROGEN  PEROXIDE,  AND  OF  THE  AMOUNT 
OF  CARBON  DIOXIDE  IN  SODIUM  CARBONATE 

G.  LUNGE  l  has  described  methods  for  the  deter- 
mination of  the  strength  of  chloride  of  lime,  pyrolu- 
site,  potassium  permanganate,  and  hydrogen  peroxide 
in  his  volumeter,  and  his  directions  are  given  below. 

All  of  these  determinations  may  be  made  with 
ease  and  accuracy  with  the  apparatus  shown  in  Fig. 
41,  on  p.  73. 

CHLORIDE  OF  LIME 

This  method  is  based  upon  the  fact  that  a  hypo- 
chlorite,  when  mixed  with  hydrogen  peroxide,  imme- 
diately gives  up  its  active  oxygen,  as  does  the 
hydrogen  peroxide;  and  the  amount  of  oxygen  set 
free  is  always  exactly  equal  to  twice  the  amount  of 
active  oxygen  present  in  that  substance  which  is  in 
excess.  This  is  shown  by  the  equation  — 

CaOCl2  +  H202  =  CaCl2  +  H2O  +  O2. 

1  Berichte  der  deutschen  chemischen  Gesellschaft,  1885,  1872  ; 
1886,  868 ;  Zeitschr.  f.  angewandte  Chemie,  1890,  6. 

468 


CHAP,  xviii     EVALUATION   OF   CHLORIDE   OF  LIME     469 

It  is  possible  by  this  method  to  determine  the 
strength  of  chloride  of  lime  by  the  use  of  an  excess 
of  hydrogen  peroxide  of  any  unknown  strength,  and 
also  to  determine  the  strength  of  hydrogen  peroxide 
by  the  use  of  an  excess  of  chloride  of  lime. 

A  (turbid)  solution  of  chloride  of  lime  is  made 
in  the  usual  manner  by  shaking  10  g.  of  the  sub- 
stance with  250  ccm.  of  water.  5  ccm.  of  this  solu- 
tion, corresponding  to  0.2  g.  of  the  substance,  is 
then  removed  with  a  pipette,  and  placed  in  the  small 
bottle  q  of  the  evolution  apparatus  (Fig.  41).  In 
the  inner  tube  o  is  placed  an  excess  of  hydrogen  per- 
oxide. 2  ccm.  of  the  commercial  hydrogen  perox- 
ide will  suffice,  for  that  contains  an  amount  of  active 
oxygen  nearly  equal  to  ten  times  its  volume.  The 
amount  of  hydrogen  peroxide  need  not  be  accurately 
measured,  and  its  strength  need  not  be  known. 

The  measuring  tube  A  is  now  filled  nearly  to  its 
wider  portion  with  mercury,  and  the  evolution 
bottle  is  connected  with  the  burette  and  immersed 
in  a  beaker  of  water.  The  mercury  is  brought  to 
the  same  height  in  the  two  arms  of  the  manometer, 
and  the  initial  volume  of  gas  is  now  read  off  on  the 
burette.  The  bottle  q  is  now  lifted  out  from  the 
beaker^  and  the  hydrogen  peroxide  is  caused  to  mix 
with  the  solution  of  chloride  of  lime  by  tipping  the 
bottle.  The  bottle  is  then  shaken  for  two  minutes, 
again  placed  in  the  beaker  of  water,  and  the  gas  vol- 
ume in  the  burette  is  read  once  more. 

When  an  excess  of  hydrogen  peroxide  acts  upon 
chloride  of  lime,  there  is  set  free  a  volume  of  oxy- 
gen equal  to  twice  that  contained  in  the  chloride  of 
lime.  Every  two  volumes  of  oxygen  correspond  to 


470  GAS   ANALYSIS  PART  m 

two  volumes  of  active  chlorine.  Therefore  the  oxy- 
gen which  is  set  free  shows  directly  the  amount  of 
active  chlorine  in  the  bleaching  powder ;  that  is,  each 
cubic  centimeter  of  evolved  gas  corresponds  to  a 
cubic  centimeter  of  a  chlorine  gas. 

If  7.917  g.  of  bleaching  powder  is  used,  and  if  this 
is  dissolved  in  250  com.  of  water,  and  5  ccm.  of  that 
solution  is  taken  for  the  determination,  then  every 
cubic  centimeter  of  evolved  gas  corresponds  to  2  per 
cent  of  chlorine  in  the  substance. 

Lunge  adds  that  the  hydrogen  peroxide,  to  give  ac- 
curate results,  must  not  be  too  concentrated.  One 
ccm.  of  it  should  set  free  not  more  than  7  ccm.  of 
oxygen  when  mixed  with  an  excess  of  chloride  of 
lime.  The  reading  of  the  evolved  gas  should  be 
made  at  once,  since  hydrogen  peroxide  will  of  itself 
slowly  set  free  small  quantities  of  oxygen. 

PYROLUSITE 

In  the  analysis  of.  pyrolusite,  the  finely  powdered 
substance  is  placed  in  the  outer  space  of  the  small 
bottle  (Fig.  41),  and  is  first  shaken  with  some  dilute 
sulphuric  acid  for  the  purpose  of  decomposing  any 
carbonates  which  may  be  present.  The  necessary 
amount  of  hydrogen  peroxide  is  then  poured  into 
the  inner  tube,  the  bottle  is  closed,  and  the  connec- 
tion with  the  burette  and  the  readings  of  the  initial 
gas  volume  are  carried  out  as  above  described.  The 
bottle  is  then  tipped  until  the  hydrogen  peroxide 
flows  out  upon  the  substance,  and  the  contents  is 
shaken  until  the  colour  of  the  residue  shows  that  the 
pyrolusite  has  been  completely  decomposed.  In  the 


CHAP,  xvin      EVALUATION   OF  CHLORIDE   OF  LIME     471 

analysis  of  Weldon  mud  the  reaction  takes  place  at 
once. 

The  reaction  proceeds  according  to  the  equation  :  — . 

Mn02  +  H202  +  H2S04  =  MnSO4  +  2  H2O  +  O2. 

Since  only  half  of  the  evolved  oxygen  comes  from 
the  pyrolusite,  1  ccm.  of  the  gas  corresponds  to 
0.003897  g.  MnO2.  If,  therefore,  0.3897  g.  of  pyro- 
lusite is  taken  for  the  analysis,  the  number  of  cubic 
centimeters  of  evolved  oxygen  corresponds  directly 
to  the  per  cent  of  MriO2  present  in  the  substance. 

POTASSIUM  PERMANGANATE 

The  strength  of  a  solution  of  potassium  permanga- 
nate is  determined  by  placing  in  a  bottle  a  measured 
amount  of-  the  potassium  permanganate  solution,  con- 
taining quite  a  little  free  sulphuric  acid,  and  intro- 
ducing into  the  tube  o  an  excess  of  hydrogen  peroxide. 
When  these  two  solutions  are  brought  together,  the 
total  active  oxygen  of  the  potassium  permanganate 
and  an  equal  volume  of  oxygen  from  the  hydrogen 
peroxide  are  at  once  set  free.  The  reaction  pro- 
ceeds according  to  the  equation  :  — 

5  H2O2  +  2  KMnO4  +  3  H2SO4  =  8  H2O  +  K2SO4 
+  2MnSO4  +  5O2. 

1  ccm.  of  oxygen  weighs  1.43003  mg.,  hence  every 
cubic  centimeter  of  the  gas  measured  at  0°  and 
under  760  mm.  pressure  corresponds  to  2.8243  mg. 
KMnO4,  according  to  the  equation  :  — 

5  O  :  KMnO4  =  80  :  158  =  1.43003  :  x, 
x  =  2.8243  mg.  KMnO4. 


472  GAS   ANALYSIS  PART  in 

If  it  is  desired  to  set  free  about  50  ccm.  of  gas, 
about  40  ccm.  of  tenth  normal  of  potassium  perman- 
ganate solution  should  be  used. 

The  Determination  of  Hydrogen  Peroxide  is  carried 
out  in  exactly  the  same  manner  as  described  for 
potassium  permanganate,  except  that  in  this  case  an 
excess  of  potassium  permanganate  is  employed. 

Since  1  ccm.  of  oxygen  weighs  1.43003  mg.,  1 
ccm.  of  the  gas  at  0°  and  760  mm.  pressure  corre- 
sponds to  1.5194  mg.  of  H2O2,  according  to  the 
equation :  — 

O2  :  H2O2  =  32  :  34  =  1.43003  :  x, 
z=  1.5194  mg. 

If  commercial  hydrogen  peroxide  of  the  strength 
of  about  2  per  cent  is  employed,  3  to  4  ccm.  of  this 
solution  will  evolve  about  50  ccm.  of  gas. 

In  similar  manner,  we  may  determine  persulphuric 
acid,  perchromic  acid,  percarbonic  acid,  periodic  acid, 
perchloric  acid,  zinc  dust,  ferrum  reductum,  lead 
dioxide,  potassium  ferricyanide,  etc. 

THE  DETERMINATION  OF  BICARBONATE  CARBON 
DIOXIDE  IN  SODIUM  CARBONATE 

Lunge  has  described  a  very  simple  apparatus  for 
the  determination  of  the  bicarbonate  carbon  dioxide 
in  sodium  carbonate. 

A  glass  tube  (Fig.  136),  65  mm.  long  and  6  mm. 
internal  diameter,  is  widened  at  one  end  and  there 
closed  by  a  ground-glass  stopper  a.  To  the  other 
end  of  the  tube  is  fastened  a  capillary  tube  d  60  mm. 
long.  To  the  interior  end  of  the  stopper  a  is  at- 
tached a  glass  rod  6,  about  30  mm.  long  and  fitting 


CHAP,  xviii     EVALUATION   OF  CHLORIDE   OF  LIME     473 

rather  tightly  into  the  glass  tube,  but  not  ground 
into  it.  The  free  space  in  the  tube  is  thus  35  mm. 
long  and  6  mm.  wide.  The  further  end  of  this 
space,  where  the  capillary  is  attached,  is  closed  by  a 
little  asbestos  or  glass-wool.  The  space  holds  about 
0.850  g.  of  pulverised  sodium  bicarbonate,  an  amount 
which  in  good  material  will  set  free  rather  more  than 
110  com.  of  carbon  dioxide  at  0°  and  760  mm.  If 
this  amount  is  either  too  large  or  too  small  for  the 
measuring  apparatus  that  is  employed,  the  space  e 


FIG.  136. 


may  be  increased  in  size  by  cutting  off  the  end  of 
the  glass  rod  £>,  or  may  be  diminished  by  the  in- 
troduction of  more  asbestos  or  glass-wool.  The 
heating  of  the  tube  is  effected  in  an  air-bath  e,  made 
from  an  iron  crucible  by  boring  two  holes  through 
its  sides.  The  crucible  is  covered  with  an  asbestos 
sheet  /",  through  which  passes  the  thermometer  g. 
A  sheet  of  asbestos  h  projects  downward  to  the  bot- 
tom of  the  flame  by  which  the  crucible  is  heated, 
and  thus  protects  the  measuring  apparatus  from  the 
heat  of  the  flame.  This  measuring  apparatus  is 
joined  to  the  end  of  the  capillary  tube  d.  A  Lunge 


474  GAS  ANALYSIS  PART  in 

gas  volumeter  or  other  suitable  measuring  burette 
may  be  employed. 

The  operation  is  carried  out  as  follows :  the  tube 
is  weighed  empty  and  is  then  filled  with  bicarbonate, 
care  being  taken  that  no  substance  remains  clinging 
to  the  walls  of  the  tube  around  a  and  b.  The  stop- 
per is  then  tightly  inserted,  and  the  tube  is  weighed 
again.  It  is  then  placed  in  the  air-bath,  in  the  posi- 
tion shown  in  the  figure,  that  part  of  the  tube  which 
contains  the  substance  lying  wholly  within  the  air- 
bath.  The  measuring  apparatus  is  then  attached  to 
d,  the  top  of  the  burette  is  opened,  and  the  air-bath 
is  heated  with  a  fairly  large  flame  until  the  thermom- 
eter stands  between  260°  and  270°.  This  usually 
takes  about  seven  minutes.  The  heating  is  then  con- 
tinued for  three  minutes  longer.  The  stopcock  of 
the  measuring  tube  is  then  closed,  and,  after  allow- 
ing the  apparatus  to  cool  for  ten  minutes,  the  gas 
volume  is  read  off. 

1  ccm.  CO2  at  760  mm.  and  0°  =  0.00196633  g.  CO2 
=  0.0075124  g.  NaHCO3. 

In  this  way  the  actual  amount  of  bicarbonate  pres- 
ent is  ascertained.  To  determine  the  amount  of 
monocarbonate,  the  total  carbon  dioxide  is  set  free 
by  treatment  with  an  acid,  and  is  measured.  The 
difference  between  the  bicarbonate  carbon  dioxide 
and  the  total  carbon  dioxide  gives  the  carbon  diox- 
ide of  the  monocarbonate.  The  total  carbon  dioxide 
in  sodium  bicarbonate  should  amount  to  at  least 
50  per  cent;  theoretically  it  is  52.38  per  cent. 


TABLE   OF   ATOMIC   WEIGHTS   OF   THE 
ELEMENTS 

(F.  W.  CLARKE) 


Aluminum 
Antimony 
Argon 
Arsenic   . 
Barium  . 
Bismuth  . 
Boron 
Bromine . 
Cadmium 
Calcium  . 
Carbon    . 
Cerium    . 
Cesium    . 
Chlorine  . 
Chromium 
Cobalt     . 
Columbium     . 
Copper    . 
Erbium  . 
Fluorine  . 
Gadolinium    . 
Gallium  . 
Germanium    . 
Glucinum 
Gold 

Helium  . 
Hydrogen 
Indium  . 
Iodine 
Indium  . 
Iron 

Lanthanum     . 
Lead 
Lithium  . 
Magnesium     . 
Manganese 
Mercury  . 


26.9 

Molybdenum    . 

119.5 

Neodymiuin 

9 

Nickel 

74.45 

Nitrogen  . 

136.4 

Osmium    . 

206.5 

Oxygen     . 

10.9 

Palladium 

79.34 

Phosphorus 

111.55 

Platinum  . 

39.8 

Potassium 

11.9 

Praseodymium 

138.0 

Rhodium  . 

131.9 

Rubidium 

35.18 

Ruthenium 

51.7 

Samarium 

58.55 

Scandium 

93.0 

Selenium  . 

63.1 

Silicon 

164.7 

Silver 

18.9 

Sodium     . 

155.8 

Strontium 

69.5 

Sulphur    . 

71.9 

Tantalum 

9.0 

Tellurium 

195.7 

Terbium  . 

? 

Thallium  . 

1.000 

Thorium  . 

113.1 

Thulium  . 

125.89 

Tin    . 

191.7 

Titanium  . 

55.6 

Tungsten  . 

137.6 

Uranium  . 

205.36 

Vanadium 

6.97 

Ytterbium 

24.1 

Yttrium    . 

54.6 

Zinc  . 

198.50 

Zirconium 

475 

95.3 
142.5 
58.25 
13.93 
189.6 
15.88 
106.2 
30.75 
193.4 
38.82 
139.4 
102.2 
84.75 
100.9 
149.2 
43.8 
78.6 
28.2 
107.11 
22.88 
86.95 
31.83 
181.5 
126.5 
158.8 
202.61 
2.'30.8 
169.4 
118.1 
47.8 
182.6 
237.8 
51.0 
171.9 
88.3 
64.9 
89.7 


Reduction  of  a  Gas  Volume  to  o°  and  760  mm. 

If  "Pis  the  volume  of  a  gas  at  t°  and  h  mm.  pressure  of 
mercury,  then  at  0°  and  760  mm.  pressure  the  volume 

F=  V  h 

1  +  0.003670*760 

Value  of  (1  +  0.003670 1)  for  t  =  -  2  to  +  4°. 


t 

1+0.003670  1 

LO£T      1 

t 

1+0.003670;! 

T         1 

*  1+0.003670  t 

g  1+0.003670  t 

o, 

o, 

1, 

9,      —10 

-2°.0 

99266 

00320 

l°.l 

00404 

99825 

-1.9 

99303 

00304 

1.2 

00440 

99809 

-1.8 

99339 

00288 

1.3 

00477 

99793 

-1.7 

99376 

00272 

1.4 

00514 

99777 

-1.6 

99413 

00256 

1.5 

00551 

99761 

-1.5 

99449 

00240 

1.6 

00587 

99746 

-1.4 

99486 

00224 

1.7 

00624 

99730 

-1.3 

99523 

00208 

1.8 

00661 

99714 

-1.2 

96560 

00192 

1.9 

00697 

99698 

-1.1 

99596 

00176 

2.0 

00734 

99682 

-1.0 

99633 

00160 

1, 

9,      -10 

o, 

o, 

2.1 

00771 

99666 

-0.9 

99670 

00144 

2.2 

00807 

99651 

-0.8 

99706 

00128 

2.3 

00844 

99635 

-0.7 

99743 

00112 

2.4 

00881 

99619 

-0.6 

99780 

00096 

2.5 

00918 

99603 

-0.5 

99816 

00080 

2.6 

00954 

99588 

-0.4 

99853 

00064 

2.7 

00991 

99572 

-0.3 

99890 

00048 

2.8 

01028 

99556 

-0.2 

99927 

00032 

2.9 

01064 

99540 

-0.1 

99963 

00016 

3.0 

01101 

99524 

0.0 

100000 

00000 

1, 

9,      -10 

1, 

9,      -10 

3.1 

01138 

99509 

+0.1 

00037 

99984 

3.2 

01174 

99493 

0.2 

00073 

99968 

3.3 

01211 

99477 

0.3 

00110 

yyyo^ 

3.4 

01248 

99461 

0.4 

00147 

99936 

3.5 

01285 

99445 

0.5 

00184 

99920 

3.6 

01321 

99430 

0.6 

00220 

99905 

3.7 

01358 

99414 

0.7 

00257 

99889 

3.8 

01395 

99398 

0.8 

00294 

99873 

3.9 

01431 

99383 

0.9 

00330 

99857 

4.0 

01468 

99367 

1.0 

00367 

99841 

476 


Reduction  of  a  Gas  Volume  to  o°  and  760  mm. 
Value  of  (1  +  0.003670  t)  for  t  =  4.1  to  14.0°. 


t 

1+0.003670  t 

L°g  1+0.0086TO  t 

t 

1+0.003670  1 

Loc    1 

e  1+0.003670  t 

1, 

9,      -10 

1, 

9,      —10 

4°.l 

01505 

99351 

9°.l 

03340 

98573 

4.2 

01541 

99336 

9.2 

03376 

98558 

4.3 

01578 

99320 

9.3 

03413 

98542 

4.4 

01615 

99304 

9.4 

03450 

98527 

4.5 

01652 

99288 

9.5 

03487 

98511 

4.6 

01688 

99273 

9.6 

03523 

98496 

4.7 

01725 

99257 

9.7 

03560 

98481 

4.8 

01762 

99241 

9.8 

03597 

98465 

4.9 

01798 

99226 

9.9 

03633 

98450 

5.0 

01835 

99210 

10.0 

03670 

98435 

1, 

9,      —10 

1, 

9,       —10 

5.1 

01872 

99195 

10.1 

03707 

98420 

5.2 

01908 

99179 

10.2 

03743 

98404 

5.3 

01945 

99163 

10.3 

03780 

98389 

5.4 

01982 

99148 

10.4 

03817 

98373 

5.5 

02019 

99132 

10.5 

03854 

98358 

5.6 

02055 

99117 

10.6 

03890 

98343 

5.7 

02092 

99101 

10.7 

03927 

98327 

5.8 

02129 

99085 

10.8 

03964 

98312 

5.9 

02165 

99070 

10.9 

04000 

98297 

6-0 

02202 

99054 

11.0 

04037 

98281 

1, 

9,      -10 

1, 

9,      —10 

6.1 

02239 

99038 

11.1 

04074 

98266 

6.2 

02275 

99023 

11.2 

04110 

98251 

6.3 

02312 

99007 

11.3 

04147 

98235 

6.4 

02349 

98992 

11.4 

04184 

98220 

6.5 

02386 

98976 

11.5 

04221 

98204 

6.6 

02422 

98961 

11.6 

04257 

98189 

6.7 

02459 

98945 

11.7 

04294 

98174 

6.8 

02496 

98929 

11.8 

04331 

98159 

6.9 

02532 

98914 

11.9 

04367 

98144 

7.0 

02569 

98899 

12.0 

04404 

98128 

1, 

9,      -10 

1, 

9,       —10 

7.1 

02606 

98883 

12.1 

04441 

98113 

7.2 

02642 

98867 

12.2 

04477 

98098 

7.3 

02679 

98852 

12.3 

04514 

98083 

7.4 

02716 

98836 

12.4 

04551 

98067 

7.5 

02753 

98821 

12.5 

04588 

98052 

7.6 

02789 

98805 

12.6 

04624 

98037 

7.7 

02826 

98790 

12.7 

04661 

98022 

7.8 

02863 

98774 

12.8 

04698 

98006 

7.9 

02899 

98759 

12.9 

04734 

97991 

8.0 

02936 

98743 

13.0 

04771 

97976 

1, 

9,      —10 

1, 

9,      -10 

8.1 

02973 

98728 

13.1 

04808 

97961 

8.2 

03009 

98712 

13.2 

04844 

97945 

8.3 

03046 

98697 

13.3 

04881 

97930 

8.4 

03083 

98681 

13.4 

04918 

97915 

8.5 

03120 

98666 

13.5 

04955 

97900 

8.6 

03156 

98651 

13.6 

04991 

97885 

8.7 

03193 

98635 

13.7 

05028 

97869 

8.8 

03230 

98619 

13.8 

05065 

97854 

8.9 

03266 

98604 

13.9 

05101 

97839 

9.0 

03303 

98589 

14.0 

05138 

97824 

477 


Reduction  of  a  Gas  Volume  to  o°  and  760  mm. 

Value  of  (1  +  0.003670  t)  for  *  =  14.1  to  24.0°. 


t 

1+0.0036TO  t 

Lotr    1 

t 

1+0.003670  t 

L      1 

g  1+0.0036TO  t 

1+0.  003670  1 

1, 

9,      -10 

1, 

9,       —10 

14°.l 

05175 

97809 

19°.l 

07010 

97058 

14.2 

05211 

97794 

19.2 

07046 

97043 

14.3 

05248 

97779 

19.3 

07083 

97028 

14.4 

05285 

97763 

19.4 

07120 

97013 

14.5 

05322 

97748 

19.5 

07157 

96998 

14.6 

05358 

97733 

19.6 

07193 

96983 

14.7 

05395 

97718 

19.7 

07230 

96968 

14.8 

05432 

97703 

19.8 

07267 

96954 

14.9 

05468 

97688 

19.9 

07303 

96939 

15.0 

05505 

97673 

20.0 

07340 

96924 

1, 

9,      -10 

1, 

9,       —10 

15.1 

05542 

97657 

20.1 

07377 

96909 

15.2 

05578 

97642 

20.2 

07413 

96894 

15.3 

05615 

97627 

20.3 

07450 

96879 

15.4 

05652 

97612 

20-4 

07487 

96864 

15.5 

05689 

97597 

20.5 

07524 

96850 

15.6 

05725 

97582 

20.6 

07560 

96835 

15.7 

05762 

97567 

20.7 

07597 

96820 

15.8 

05799 

97552 

20.8 

07634 

96805 

15.9 

05835 

97537 

20.9 

07670 

96791 

16.0 

05872 

97522 

21.0 

07707 

96776 

1, 

9,      -10 

1, 

9,       —10 

16.1 

05909 

97507 

21.1 

07744 

96761 

16.2 

05945 

97492 

21.2 

07780 

96746 

16.3 

05982 

97477 

21.3 

07817 

96731 

16.4 

06019 

97462 

21.4 

07854 

96716 

16.5 

06056 

97447 

21.5 

07891 

96702 

16.6 

06092 

97432 

21.6 

07927 

96687 

16.7 

06129 

.  97417 

21.7 

07964 

96672 

16.8 

06166 

97402 

21.8 

08001 

96657 

16.9 

06202 

97387 

21.9 

08037 

96643 

17.0 

06239 

97372 

22.0 

08074 

96628 

1, 

9,      —10 

1, 

9,      -10 

17.1 

06276 

97357 

22.1 

08111 

96613 

17.2 

06312 

97342 

22.2 

08147 

96598 

17.3 

06349 

97327 

22.3 

08184 

96584 

17.4 

06386 

97312 

22.4 

08221 

96569 

17.5 

06423 

97297 

22.5 

08258 

96554 

17.6 

06459 

97282 

22.6 

08294 

96539 

17.7 

06496 

97267 

22.7 

08331 

96525 

17.8 

06533 

97252 

22.8 

08368 

96510 

17.9 

06569 

97237 

22.9 

08404 

96495 

18.0 

06606 

97222 

23.0 

084.41 

96481 

1, 

9,      —10 

1, 

9,       -10 

18.1 

06643 

97207 

23.1 

08478 

96466 

18.2 

06679 

97192  ' 

23.2 

08514 

96451 

18.3 

06716 

97177 

23.3 

08551 

96437 

18.4 

06753 

97162 

23.4 

08588 

96422 

18.5 

06790 

97147 

23.5 

08625 

96407 

18.6 

06826 

97132 

23.6 

08661 

96393 

18.7 

06863 

97117 

23.7 

08698 

96378  . 

18.8 

06900 

97102 

23.8 

08735 

96363 

18.9 

06936 

97088 

23.9 

08771 

96349 

19.0 

06973 

97073 

24.0 

08808 

96334 

478 


Reduction  of  a  Gas  Volume  to  o°  and  760  mm. 
Value  of  (1  +  0.0036700  for  t  =  24.1  to  34.0°. 


t 

1+0.003670  t 

L      1 

t 

1+0.003670  1 

Loe-     l 

K  1+0.003670  1 

e  1+0.003670  1 

1, 

9,      -10 

I, 

9,      —10 

24°.  1 

08845 

96319 

29°.l 

10680 

95593 

24.2 

08881 

96305 

29.2 

10716 

95579 

24.3 

08918 

96290 

29.3 

10753 

95565 

24.4 

08956 

96275 

29.4 

10790 

95550 

24.5 

08992 

96261 

29.5 

10827 

95535 

24.6 

09028 

96246 

29.6 

10863 

95521 

24.7 

09065 

96231 

29.7 

10900 

95507 

248 

09102 

96217 

29.8 

10937 

95492 

24.9 

09138 

96202 

29.9 

10973 

95478 

25.0 

09175 

96188 

30.0 

11010 

95464 

1, 

9,      -10 

1, 

9,       -10 

25.1 

09212 

96173 

30.1 

11047 

95449 

25.2 

09248 

96159 

30.2 

11083 

95435 

25.3 

09285 

96144 

30.3 

11120 

95421 

25.4 

09322 

96129 

30.4 

11157 

95406 

25.5 

09359 

96115 

30-5 

11194 

95392 

25.6 

09395 

96100 

30.6 

11230 

95378 

25.7 

09432 

96086 

30.7 

11267 

95363 

25.8 

09469 

96071 

30.8 

11304 

95349 

25.9 

09505 

96057 

30.9 

11340 

95335 

26.0 

09542 

96042 

31.0 

11377 

95320 

1, 

9,      -10 

1, 

9,       -10 

26.1 

09579 

96027 

31.1 

11414 

95306 

26.2 

09615 

96013 

31.2 

11450 

95292 

26.3 

09652 

95998 

31.3 

11487 

95278 

26.4 

09689 

95984 

31.4 

11524 

95263 

26.5 

09726 

95969 

31.5 

11561 

95249 

26.6 

09762 

95955 

31.6 

11597 

95235 

26.7 

09799 

95940 

31.7 

11634 

95220 

26.8 

09836 

95925 

31.8 

11671 

95206 

26.9 

09872 

95901 

31.9 

11707 

95192 

27.0 

09909 

95897 

32.0 

11744 

95178 

1, 

9,      -10 

1, 

9,       -10 

27.1 

09946 

95882 

32.1 

11781 

95163 

27.2 

09982 

95868 

32.2 

11817 

95149 

27.3 

10019 

95853 

32.3 

11854 

95135 

27.4 

10056 

95839 

32.4 

11891 

95120 

27.5 

10093 

95824 

32.5 

11928 

95106 

27.6 

10129 

95810 

32.6 

11964 

95092 

27.7 

10166 

95795 

32.7 

12001 

95078 

27.8 

10203 

95781 

32.8 

12038 

95064 

27.9 

10239 

95767 

32.9 

12074 

95049 

28.0 

10276 

95752 

33.0 

12111 

95035 

1, 

9,      —10 

1, 

9,       -10 

28.1 

10313 

95737 

33.1 

12148 

95021 

28.2 

10349 

95723 

33.2 

12184 

95007 

28.3 

10386 

95709 

33.3 

12221 

94993 

28.4 

1G423 

95694 

334 

12258 

94978 

28.5 

10460 

95679 

33.5 

12295 

94964 

28.6 

10496 

95665 

33.6 

12331 

94950 

28.7 

10533 

95651 

33.7 

12368 

94936 

28.8 

10570 

95630 

33.8 

12405 

94922 

28.9 

10606 

95622 

33.9 

12441 

94907 

29.0 

10643 

95608 

34.0 

12478 

94893 

479 


Tension  of  Aqueous  Vapour 

Expressed  in  millimeters  of  mercury  at  0°,  density  of  mercury 
=  13.59593  at  latitude  45°  and  at  the  sea-level. 

Calculated  from  Regnault's  measurements  by  Broch  (  Trav.  et  Mem. 
du  Bur.  intern,  des  Poids  et  Mes.  I  A.  33,  1881). 


t 

Tension 

t 

Tension 

t 

Tension 

t 

Tension 

mm. 

mm. 

mm. 

mm. 

-2°.0 

3.9499 

2°.6 

5.5008 

T.I 

7.5171 

11°.6 

10.1614 

-1.9 

3.9790 

2.7 

5.5398 

7.2 

7.5685 

11.7 

10.2285 

-1.8 

4.0082 

2.8 

5.5790 

7.3 

7.6202 

11.8 

10.2960 

-1.7 

4.0376 

2.9 

5.6185 

7.4 

7.6722 

11.9 

10.3639 

-1.6 

4.0672 

3.0 

5.6582 

7.5 

7.7246 

12.0 

10.4322 

-1.5 

4.0970 

7.6 

7.7772 

-1.4 

4.1271 

3.1 

5.6981 

7.7 

7.8302 

12.1 

10.5009 

-1.3 

4.1574 

3.2 

5.7383 

7.8 

7.8834 

12.2 

10.5700 

-1.2 

4.1878 

3.3 

5.7788 

7.9 

7.9370 

12.3 

10.6394 

-1.1 

4.2185 

3.4 

5.8195 

8.0 

7.9909 

12.4 

10.7093 

3.5 

5.8605 

12.5 

10.7796 

-1.0 

4.2493 

3.6 

5.9017 

8.1 

8.0452 

12.6 

10.8503 

-0.9 

4.2803 

3.7 

5.9432 

8.2 

8.0998 

12.7 

10.9214 

-0.8 

4.3116 

3.8 

5.9850 

8.3 

8.1547 

12.8 

10.9928 

-0.7 

4.3430 

3.9 

6.0270 

8.4 

8.2099 

12.9 

11.0647 

-0.6 

4.3747 

4.0 

6.0693 

8.5 

8.2655 

13.0 

11.1370 

-0.5 

4.4065 

8.6 

8.3214 

-0.4 

4.4385 

4.1 

6.1118 

8.7 

8.3777 

13.1 

11.2097 

-0.3 

4.4708 

4.2 

6.1546 

8.8 

8.4342 

13.2 

11.2829 

-0.2 

4.5032 

4.3 

6.1977 

8.9 

8.4911 

13.3 

11.3564 

-0.1 

4.5359 

4.4 

6.2410 

9.0 

8.5484 

13.4 

11.4304 

4.5 

6.2846 

13.5 

11.5048 

0.0 

4.5687 

4.6 

6.3285 

13.6 

11.5797 

+0.1 

4.6017 

4.7 

6.3727 

9.1 

8.6061 

13.7 

11.6550 

0.2 

4.6350 

4.8 

6.4171 

9.2 

8.6641 

13.8 

11.7307 

0.3 

4.6685 

4.9 

6.4618 

9.3 

8.7224 

13.9 

11.8069 

0.4 

4.7022 

5.0 

6.5067 

9.4 

8.7810 

14.0 

11.8835 

0.5 

4.7361 

9.5 

8.8400 

0.6 

4.7703 

9.6 

8.8993 

0.7 

4.8047 

5.1 

6.5519 

9.7 

8.9589 

14.1 

11.9605 

'  0.8 

4.8393 

5.2 

6.5974 

9.8 

9.0189 

14.2 

12.0380 

0.9 

4.8741 

5.3 

6.6432 

9.9 

9.0792 

14.3 

12.1159 

1.0 

4.9091 

5.4 

6.6893 

10.0 

9.1398 

14.4 

12.1943 

5.5 

6.7357 

14.5 

12.2731 

.1 

4.9443 

5.6 

6.7824 

10.1 

9.2009 

14.6 

12.3523 

.2 

4.9798 

5.7 

6.8293 

10.2 

9.2623 

14.7 

12.4320 

.3 

5.0155 

5.8 

6.8765 

10.3 

9.3241 

14.8 

12.5122 

.4 

5.0515 

5.9 

6.9240 

10.4 

9.3863 

14.9 

12.5928 

.5 

5.0877 

6.0 

6.9718 

10.5 

9.4488 

15.0 

12.6739 

.6 

5.1240 

10.6 

9.5117 

.7 

5.1606 

6.1 

7.0198 

10.7 

9.5750 

15.1 

12.7554 

1.8 

5.1975 

6.2 

7.0682 

10.8 

9.6387 

15.2 

12.8374 

1.9 

5.2346 

6.3 

7.1168 

10.9 

9.7027 

15.3 

12.9198 

2.0 

5.2719 

6.4 

7.1658 

11.0 

9.7671 

15.4 

13.0027 

6.5 

7.2150 

15.5 

13.0861 

2.1 

5.3094 

6.6 

7.2646 

11.1 

9.8318 

15.6 

13.1700 

2.2 

5.3472 

6.7 

7.3145 

11.2 

9.8969 

15.7 

13.2543 

2.3 

5.3852 

6.8 

7.3647 

11.3 

9.9624 

15.8 

13.3392 

2.4 

5.4235 

6.9 

7.4152 

11.4 

10.0283 

15.9 

13.4245 

2.5 

5.4620 

7.0 

7.4660 

11.5 

10.0946 

16.0 

13.5103 

480 


Tension  of  Aqueous  Vapour — Continued 


t 

Tension 

t 

Tension 

t 

Tension 

t 

Tension 

mm. 

mm. 

mm. 

mm. 

16°.l 

13.5965 

20°.6 

18.0176 

25°.l 

23.6579 

29°.6 

30.7928 

16  2 

13.6832 

20.7 

18.1288 

25  2 

23.7991 

29.7 

30.9707 

16  3 

13.7705 

20.8 

18.2406 

25.3 

23.9411 

29.8 

31.1494 

16-4 

13.8582 

20.9 

18.3529 

25.4 

24.0838 

29.9 

31.3291 

16.5 

13.9464 

21.0 

18.4659 

25.5 

24.2272 

30.0 

31.5096 

16.6 

14.0351 

25.6 

24.3714 

16.7 

14.1243 

21.1 

18.5795 

25.7 

24.5164 

30.1 

31.6910 

16.8 

14.2141 

21.2 

18.6937 

25.8 

24.6620 

30.2 

31.8734 

16.9 

14.3043 

21.3 

18.8085 

25.9 

24.8084 

30.3 

32.0567 

17.0 

14.3950 

21.4 

18.9240 

26.0 

24.9556 

30.4 

32.2410 

21.5 

19.0400 

30.5 

32.4262 

17.1 

14.4862 

21.6 

19.1567 

26.1 

25.1035 

30.6 

32.6124 

17.2 

14.5779 

21.7 

19.2740 

26.2 

25.2523 

30.7 

32.7995 

17.3 

14.6702 

21.8 

19.3920 

26.3 

25.4018 

30.8 

32.9875 

17.4 

14.7630 

21.9 

19.5105 

26.4 

25.5521 

30.9 

33.1765 

17.5 

14.8563 

22.0 

19.6297 

26.5 

25.7032 

31.0 

33.3664 

17.6 

14.9501 

26.6 

25.8551 

17.7 

15.0444 

22.1 

19.7496 

26.7 

26.0077 

31.1 

33.5573 

17.8 

15.1392 

22.2 

19.8701 

26.8 

26.1612 

31.2 

33.7491 

17.9 

15.2345 

22.3 

19.9912 

26.9 

26.3155 

31.3 

33.9419 

18.0 

15.3304 

22.4 

20.1130 

27.0 

26.4705 

31.4 

34.1356 

22.5 

20.2355 

31.5 

34.3303 

18.1 

15.4268 

22.6 

20.3586 

27.1 

26.6263 

31.6 

34.5259 

18.2 

15.5237 

22.7 

20.4824 

27.2 

26.7830 

31.7 

34.7225 

18.3 

15.6212 

22.8 

20.6068 

27.3 

26.9405 

31.8 

34.9201 

18.4 

15.7192 

22.9 

20.7319 

27.4 

27.0987 

31.9 

35.1186 

18.5 

15.8178 

23.0 

20.8576 

27.5 

27.2578 

32.0 

35.3181 

18.6 

15.9169 

27.6 

27.4177 

18.7 

16.0166 

23.1 

20.9840 

27.7 

27.5784 

32.1 

35.5186 

18.8 

16.1168 

23.2 

21.1110 

27.8 

27.7399 

32.2 

35.7201 

18.9 

16.2176 

23.3 

21.2388 

27.9 

27.9023 

32.3 

35.9226 

19.0 

16.3189 

23.4 

21.3672 

28.0 

28.0654 

32.4 

36.1261 

23.5 

21.4964 

32.5 

36.3307 

19.1 

16.4208 

23.6 

21.6262 

28.1 

28.2294 

32.6 

36.5363 

19.2 

16.5233 

23.7 

21.7567 

28.2 

28.3942 

32.7 

36.7429 

19.3 

16.6263 

23.8 

21.8879 

28.3 

28.5599 

32.8 

36.9505 

19.4 

16.7299 

23.9 

22.0198 

28.4 

28.7265 

32.9 

37.1592 

19.5 

16.8341 

24.0 

22.1524 

28.5 

28.8939 

33.0 

37.3689 

19.6 

16.9388 

28.6 

29.0622 

19.7 

17.0441 

24.1 

22.2857 

28.7 

29.2313 

33.1 

37.5796 

19.8 

17.1499 

24.2 

22.4196 

28.8 

29.4013 

33.2 

37.7914 

19.9 

17.2563 

24.3 

22.5543 

28.9 

29.5722 

33.3 

38.0042 

20.0 

17.3632 

24.4 

22.6898 

29.0 

29.7439 

33.4 

38.2180 

24.5 

22.8259 

33.5 

38.4329 

20.1 

17.4707 

24.6 

22.9628 

29.1 

29.9165 

33.6 

38.6488 

20.2 

17.5789 

24.7 

23.1003 

29.2 

30.0900 

33.7 

38.8657 

20.3 

17.6877 

24.8 

23.2386 

29.3 

30.2644 

33.8 

39.0837 

20.4 

17.7971 

24.9 

23.3777 

29.4 

30.4396 

33.9 

39.3027 

20.5 

17.9071 

25.0 

23.5174 

29.5 

30.6157 

34.0 

39.5228 

481 


Theoretical  Densities  of  Gases 

And  weights  of  one  liter  of  the  same  at  0°  and  760°  mm.  pressure, 
for  latitude  45°  and  that  of  Berlin 


Density 

Weight  of  1  liter 

in  grams 

Substance 

Formula 

Hydrogen 
=  2 
(Mol.  Wt.) 

Air  =  l 

Latitude  45° 
at  sea-level 

In  Berlin 

Acetylene  .... 

C2H2 

25.947 

0.89820 

1.16143 

1.16219 

Allylene     .... 

C3H4 

39.921 

1.38194 

1.78692 

1.78811 

Ammonia  .... 

NH3 

17.012 

0.58890 

0.76148 

0.76199 

Arsine 

AsH3 

77  918 

2.69728 

Bromine    .... 

Br2 

159i538 

5^52271 

7.14115 

7^14588 

Butane 

f1  TT 

57  894 

2.00411 

9  *>Q149 

9  W31J. 

Butylene    .... 

C44Hg 

55^894 

L93488 

^.Ut7J-4:^ 

2.50190 

•Z.OV/Olrr 

2.50355 

Carbon  dioxide  .     . 

C02 

43.900 

1.51968 

1.96503 

1.96633 

Carbon  monoxide  . 

CO 

27.937 

0.96709 

1.25050 

1.25133 

Carbon  oxysulphide 

COS 

59.937 

2.07483 

2.68287 

2.68464 

Carbonyl  chloride  . 

COC12 

98.689 

3.41631 

4.41746 

4.42039 

Chlorine     .... 

C12 

70.752 

2.44921 

3.16696 

3.16906 

Cyanogen  .... 

C2N2 

51.971 

1.79907 

2.32630 

2.32784 

Ethane  ... 

C^  TT 

29.947 

1  03667 

1.34047 

Ethylene    .... 

V-'2J"16 

27.947 

0196744 

L25095 

1.25178 

Hydriodic  acid  .     . 

HI4 

127.559 

4.41570 

5.70972 

5.71351 

Hydrobromic  acid  . 

HBr 

80.769 

2.79597 

3.61534 

3.61773 

Hydrochloric  acid  . 

HC1 

36.376 

1.25922 

1.62824 

1.62932 

Hydrofluoric  acid  . 

HF 

19.984 

0.69178 

0.89451 

0.89511 

Hydrogen  .... 

H2 

2.000 

0.069234 

0.089523 

0.089582 

Hydrogen  selenide  . 

H2Se 

80.797 

2.79694 

3.61659 

3.61899 

Hydrogen  sulphide 

H2S 

34.000 

1.17697 

1.52189 

1.52290 

Hydrogen  telluride 

H2Te 

129.960 

4.49881 

5.81720 

5.82105 

Methane    .... 

CH4 

15.974 

0.55297 

0.71502 

0.71549 

Nitric  oxide   .     .     . 

NO 

29.975 

1.03764 

1.34172 

1.34261 

Nitrogen    .... 

N2 

28.024 

0.97010 

1.25440 

1.25523 

Nitrous  oxide     .     . 

N20 

43.987 

1.52269 

1.96892 

1.97023 

Oxygen      .... 

02 

31.927 

1.10521 

1.42908 

1.43003 

Phosphine  .... 

PH3 

33.958 

1.17552 

1.52001 

1.52102 

Propane     .... 

C3H8 

43.921 

1.52041 

1.96597 

1.96727 

Propylene  .... 

41.921 

1.45118 

1.87644 

1.87769 

Silicon  tetrafluoride 

S?F4 

104.131 

3.60469 

4.66105 

4.66414 

Sulphur  dioxide 

S02 

63.927 

2.21295 

2.86146 

2.86336 

Water  vapour    .     . 

H20 

17.963 

0.62182 

0.80405 

0.80458 

Atmospheric  air 

- 

1.00000 

1.293052 

1.293909 

482 


INDEX   TO   SUBJECTS 


Absorbents,  solubility  of  gases  in, 

119. 

Absorption  apparatus,  106. 
Absorption -apparatus,  Reiset,  110. 
Absorption    apparatus,    Winkler, 

109. 

Absorption  pipettes,  47. 
Absorption     pipette,      connection 

with  gas  burette,  54. 
Absorption  pipette,  double,  50. 
Absorption    pipette,    double,    for 

solid  and  liquid  reagents,  51. 
Absorption  pipette,  for  exact  gas 

analysis,  67,  68,.  69. 
Absorption  pipette,  manipulation 

of,  53. 

Absorption  pipette,  simple,  48. 
Absorption     pipette,    simple,    for 

solid  and  liquid  reagents,  49. 
Absorption  tube,  Pettenkofer,  108. 
Absorption  tube,  Winkler,  108. 
Accuracy  of  technical  analysis,  115. 
Acetylene  gas,  analysis  of,  312. 
Acetylene,  properties  of,  231. 
Air-pump,  Topler,  393. 
Ammonia,  199. 
Ammonia,    determination    of,   in 

illuminating  gas,  308. 
Analysis  of  gases,  general  remarks 

upon,  32. 

Analytical  absorbing  power  of  re- 
agents, 144. 

Apparatus,  making  of,  105. 
Aqueous  vapour,  determination  of, 

in  air,  333. 
Argon,  168. 

Argon,  separation  of,  from  air,  170. 
Argon  group,  gases  of  the,  168. 
Arsiue,  250. 


Aspirator,  brass  suction  pump,  25. 

Aspirator,  rubber  bulb,  24. 

Aspirator,  sheet  zinc,  26. 

Aspirator,  steam,  25. 

Aspirator,  water  suction  pumps,  25. 

Atmospheric  air,  analysis  of,  333. 

Atomic  weights  of  elements,  table 
of,  475. 

Autoclave,  for  determining  heat- 
ing power  of  fuel,  418. 

B 

Bacteria,  gases  produced  by,  376. 
Battery,  Bunsen,135. 
Blast-furnace  gases,  263. 
Bleaching  powder,  gases  in  manu- 
facture of,  330. 


Calorimeter  for  determining  heat- 
ing power  of  fuel,  425. 

Calorimeter,  the  flame,  442. 

Capillary,  connecting,  with  funnel 
tube,  70. 

Carbon,  determination  of,  in  or- 
ganic substances,  392. 

Carbon  dioxide,  201. 

Carbon  dioxide,  determination  of, 
in  air,  336. 

Carbon  dioxide,  determination  of, 
in  air,  by  Hesse's  method,  337. 

Carbon  dioxide,  determination  of, 
in  air,  by  Pettersson's  method, 
346. 

Carbon  dioxide,  determination  of, 
in  air,  by  Pettersson-Palmqvist 
method,  363. 

Carbon  dioxide,  determination  of, 
in  illuminating  gas,  309. 


483 


484 


INDEX   TO   SUBJECTS 


Carbon  dioxide  in  sodium  carbon- 
ate, determination  of,  472. 

Carbon  in  iron,  volumetric  deter- 
mination of,  459. 

Carbon  monoxide,  202. 

Carbon  monoxide,  absorption  of, 
by  nitric  acid,  211. 

Carbon  monoxide,  detection  of,  by 
Kostin's  method,  225. 

Carbon  monoxide,  detection  of, 
witb  blood,  211. 

Carbon  monoxide,  detection  of, 
with  palladium  chloride,  210. 

Carbon  monoxide,  determination 
of,  by  cuprous  chloride,  206. 

Carbon  monoxide,  determination 
of,  in  air,  370. 

Carbon  oxysulphide,  241. 

Chloride  of  lime,  evaluation  of, 
468. 

Chlorine,  244. 

Chlorine,  determination  of,  in 
chamber-air,  330. 

Chlorine,  determination  of,  in  pres- 
ence of  hydrochloric  acid  gas, 
331. 

Coke-furnace  gases,  263. 

Collecting  of  gases  absorbed  in 
liquids,  10,  13. 

Collecting  of  gases  from  blast- 
furnace, 22. 

Collecting  of  gases  from  furnaces, 
3. 

Collecting  of  gases  from  lead  fur- 
naces, 22. 

Collecting  of  gases  from  reactions 
in  sealed  tubes,  15. 

Collecting  of  gases  from  spring 
water,  8,  9. 

Collecting  of  gases,  general  re- 
marks upon  the,  3. 

Collecting  of  gases  in  bottles,  4. 

Collecting  of  gases  in  glass  tubes,  6. 

Collecting  of  gases  present  in  min- 
erals, 16, 18. 

Combustion  gases,  255. 

Combustion  of  gases,  calculation 
of  results  in,  122. 


Combustion  tube,  capillary,  Dreh- 

schmidt,  140. 
Combustion  of  gases,  formation  of 

oxides  of  nitrogen  in,  127. 
Combustion  of  gases,  limits  of  ex- 

plosibility  in,  128. 
Combustion  pipette,  Dennis,  138. 
Confining  liquid,  running  down  of, 

116. 

Copper-acetylene,  232. 
Cuprous  chloride,  preparation  of, 

203. 
Cyanogen,  233. 

D 
Densities  of  Gases,  table  of,  482. 


Electrolysis   of    chlorides,    gases 

from,  328. 
Ethylene,  228. 
Evolution  apparatus,  71,  74. 
Exact  gas  analysis,  apparatus  for, 

59. 
Exact  gas  analysis,  apparatus  for, 

without  stopcocks,  76. 
Exact  gas  analysis,  apparatus  for, 

with  stopcocks,  59. 
Exact  gas  analysis,  correction  tube 

for,  94. 
Exact  gas  analysis,  filling  pipettes 

for,  86. 
Exact  gas  analysis,  gas  pipettes 

for,  84,  88,  89. 
Exact  gas  analysis,  measurement 

of  gas  volume  in,  81. 
Exact  gas  analysis,  measuring  bulb 

for,  81. 

Exact  gas  analysis,  method  of  ab- 
sorption in,  89. 
Explosion  pipette,  for   exact  gas 

analysis,  132. 
Explosion  pipette,  for  technical  gas 

analysis,  130. 


Flame  calorimeter,  442. 
Flame  test  for  detection  and  de- 
termination of  methane,  448. 


INDEX  TO  SUBJECTS 


485 


Flue  gases,  225. 

Fluorine,  determination  of,  378. 

Fluorine,     determination     of,    in 

teeth,  383. 

Fractional  combustion,  178. 
Fuel,  heating  power  of,  411. 
Furnace  gases,  255. 


Gas  balance  of  Arndt,  261. 

Gas  balance  of  Lux,  272. 

Gas  burette,  Bunte,  42. 

Gas  burette,  Honigmann,  41. 

Gas  burette,  manipulation  of  the 

simple,  36. 

Gas  burette,  modified  Winkler,  39. 
Gas  burette,  simple,  34. 
Gas  burette,  with  correction  for 

temperature  and  pressure,  59. 
Gases,   determination    of  heating 

power  of,  435. 
Gas  lantern,  for   controlling  gas 

processes,  452. 
Generator  gas,  263. 
Generator  gas,  analysis  of,  290. 
Gun-cotton,  analysis  of,  386. 


Heating  power  of  fuel,  calculation 
of,  430. 

Heating  power  of  fuel,  determina- 
tion of,  411. 

Heating  power  of  gases,  determina- 
tion of,  435. 

Helium,  168. 

Hydrocarbon  vapours,  determina- 
tion of,  in  illuminating  gas, 
277. 

Hydrochloric  acid,  246. 

Hydrocyanic  acid,  234. 

Hydrogen,  175. 

Hydrogen,  absorption  of,  by  potas- 
sium and  sodium,  193. 

Hydrogen,  determination  of,  by 
explosion,  176. 

Hydrogen,  determination  of,  by 
fractional  combustion,  178. 

Hydrogen,    determination    of,  by 


method  of  Dennis  and  Hopkins, 

177. 
Hydrogen,    determination   of,   by 

palladium,  181. 
Hydrogen,    determination    of,    in 

organic  substances,  392. 
Hydrogen  peroxide,  determination 

of,  472. 
Hydrogen  pipette,  for  exact  gas 

analysis,  133. 
Hydrogen    pipette,    for   technical 

analysis,  131. 
Hydrogen  sulphide,  235. 


Illuminating  gas,  263. 
Illuminating  gas,  determination  of 

ammonia  in,  308. 
Illuminating  gas,  determination  of 

carbon  dioxide  in,  309. 
Illuminating  gas,  determination  of 

hydrocarbon  vapours  in,  277. 
Illuminating  gas,  determination  of 

sulphur  iu,  303. 
Illuminating  gas,  determination  of 

tar  in,  273. 
Illuminating     gas,     measurement 

of   the    illuminating   power    of, 

264. 

Illuminating  gas,  volumetric  analy- 
sis of,  282. 
Illuminating  power  of  illuminat- 

gas,  measurement  of,  264. 
Induction  coil,  137. 
Iron,  volumetric  determination  of 

carbon  in,  459. 


Keeping  of  gases,  general  remarks 
upon  the,  26,  27. 

Keeping  of  gases  in  glass  receivers, 
27,  28,  29. 

Keeping  of  gases  in  glass  tubes 
with  stopcocks,  26. 

Keeping  of  gases  in  metallic  ga- 
someters, 30. 

Keeping  of  gases  over  mercury, 
27,28. 


486 


INDEX  TO   SUBJECTS 


Keeping  of  gases,  worthlessness  of 

rubber  sacks  for  the,  27. 
Krypton,  168. 

L 
Laboratory,  arrangement  of,  97. 

M 

Measurement  of  gases,  general  re- 
marks upon  the,  32. 

Mercury,  distillation  of,  in  vac- 
uum, 99. 

Mercury,  purification  of,  by  air,  103. 

Mercury,  purification  of,  by  nitric 
acid,  102. 

Mercury,,  purification  of,  by  sul- 
phuric acid  and  mercurous  sul- 
phate, 103. 

Methane,  227.    • 

Methane,  detection  and  determina- 
tion of,  by  flame  test,  448. 

Methyl-amine,  200. 

N 

Neon,  168. 

Nitric  oxide,  197. 

Nitric  oxide,  determination  of,  in 
chamber  gases,  326. 

Nitrogen,  164,  375. 

Nitrogen,  absorption  of,  167. 

Nitrogen,  determination  of,  in  or- 
ganic substances,  392. 

Nitrogen  peroxide,  determination 
of,  in  chamber  gases,  327. 

Nitrogen,  removal  of,  from  air,  170. 

Nitrogen  tetroxide,  199. 

Nitrogen  trioxide,  198. 

Nitrogen  trioxide,  determination 
of,  in  chamber  gases,  326. 

Nitro-glycerin,  analysis  of,  386. 

Nitrometer,  Hempel,  387. 

Nitrous  oxide,  195. 

Nitrous  oxide,  determination  of,  in 
chamber  gases,  326. 

O 

Organic  substances,   analysis   of, 

392. 
Orsat  apparatus,  257. 


Orsat  apparatus,  errors  of,  260. 

Oxygen,  145. 

Oxygen,  determination  of,  by  alka- 
line pyrogallol,  149. 

Oxygen,  determination  of,  by  chro- 
mous  chloride,  154. 

Oxygen  determination  of,  by  com- 
bustion, 146. 

Oxygen,  determination  of,  by 
copper,  158. 

Oxygen,  determination  of,  by  phos- 
phorus, 155. 

Oxygen,  determination  of,  in  air, 
370. 

Oxygen,  determination  of,  in 
chamber  gases,  327. 

Oxyhydrogen  gas  generator,  134. 

Ozone,  161. 

P 

Phosphine,  249. 
Photometer,  266. 

Potassium    permanganate,    deter- 
mination of,  471. 
Pyrolusite,  evaluation  of,  470. 


Running  down  of  confining  liquid, 
116. 

S 

Safety  lamp,  449. 

Saltpeter,  analysis  of,  386. 

Silicon  tetrafluoride,  248. 

Solubility  of  gases  in  absorbents, 
119. 

Specific  gravity  of  gases,  deter- 
mination of,  by  Bunsen's  method, 
268. 

Specific  gravity  of  gases,  deter- 
mination of,  with  Lux's  appa- 
ratus, 272. 

Specific  gravity  of  gases,  deter- 
mination of,  with  Schilling's  ap- 
paratus, 271. 

Stibine,  251. 

Sulphur,  determination  of,  in  il- 
luminating gas,  303. 

Sulphur  dioxide,  239, 


1KDEX   TO   SUBJECTS 


487 


Sulphur  dioxide,  detection  of,  in 

air,  374. 
Sulphur  dioxide,  determination  of, 

in  kiln  gases,  322. 
Sulphur  dioxide,  determination  of, 

in  presence  of  sulphur  trioxide, 

325. 
Sulphuric    acid,    detection    of,    in 

air,  374. 
Sulphuric  acid  manufacture,  gases 

of,  322. 

Sulphur  in  coal,  determination  of, 
444. 


Sulphur  in  organic  substances,  de- 
termination of,  444. 

T 

Tar,  determination  of,  in  illuminat- 
ing gas,  273. 
Teeth,  analysis  of,  383. 
Technical    analysis,   accuracy   of 
115. 

W 
Water  gas,  263. 

X 

Xenon,  168. 


INDEX   OF   NAMES 


Arndt,  262. 
August,  334. 

B 

Berthelot,  411,  414,  430,  444. 

Brodhun,  267. 

Bunsen,  4,  8, 13,  15,  22, 76, 122, 

133,  135,  146,  147,  165,  175, 

201,  202,  227,  228,  236,  238, 

277. 
Bunte,  42,  303. 

C 

Carius,  146,  165, 195,  202,  228. 
Cavendish,  166. 
Chapman,  25. 
Clowes,  449. 
Coquillion,  138. 
Crafts,  103. 
Crookes,  170. 
St.  Claire-Deville,  278. 
Crum,  386. 

D 

de  la  Harpe,  226. 
Dennis,  138, 139,  177,  260,  279, 

290,  293. 

Dietrich,  72,  200. 
Dittmar,  13,  247. 
Divers,  198. 
Doyere,  47,  76,  77,  84. 
Drehschmidt,  140, 141,  206, 210, 

290,303. 
Dulong,  430. 
Dupasquier,  237. 

E 

Edgar,  260. 
Elsler,  265. 
Engler,  163,  164. 
Erdmann,  166, 170. 
Erlwein,  163. 
Ettling,  84. 


127, 
195, 
268, 


287, 


287 


Favre,  441. 
Finkener,  25,  72. 
Fischer,  F.,  411,  432. 
Fresenius,  129,  237,  246,  248 

Q 

Gautier,  226. 
Geissler,  25. 
Gerstenhofer,  324. 


Hafner-Alteneck,  266. 
Hagen,  389. 
Sammarsten,  447. 
Harbeck,  4,  281. 
Hautefeuille,  194. 
Henry,  178. 
Hesse,  W.,  337,  376. 
Hofmann,  304. 
Honigmann,  41. 
Hopkins,  177,  293. 
Hoppe-Seyler,  13. 
Houzeau,  161. 
Hunefeld,  224. 

I 

Ilosvay,  128. 

J 

Jacobsen,  15. 
Jacquelain,  193. 
Jaderholm,  222. 
Jolly,  148,  158,  370. 
Junker,  435. 

K 

Reiser,  232. 
Kinnicutt,  266. 
Knoop,  71. 
Korting,  25. 
Kostin,  160,  225,  226. 
Kretz,  455. 
Kreusler,  148,  149,  370,  374. 


489 


490 


INDEX   OF   NAMES 


Kunkel,  226. 
Kunz-Krause,  233,  234. 

L 

Lautemann,  400. 

Le  Chatelier,  449. 

Levol,  146. 

Linderaann,  155, 157. 

Lubarsch,  197. 

Lumraer,  267. 

Lunge,  4,  281,  324,  325,  327,  330 

386,  468,  472. 
Lux,  272. 

M 

Mallard,  449. 
Maquenne,  166. 
Markel,  209. 
Maumene,  103. 
Moissan,  154. 
Morley,  147,  370. 


Nasse,  164. 
Neumann,  331. 
Nicloux,  226. 


N 


Oettel,  149,  374,  378. 
Orsat,  79,  140,257. 


Palmqviet,  363. 

Pauli,  201. 

Pettenkofer,  108, 112,  336. 

Pettersson,  15,  59, 145, 165, 334, 346, 

363,364. 
Pfister,  334. 
Pieler,  449. 
Playfair,  22. 
Preusse,  10. 

B 

Ramsay,  9,  16,  166,  170. 
Rayleigh,  166,  170. 
Reich,  241,  322. 
Reichardt,  10. 
Reiset,  110. 
Reverdine,  226. 
Riban,  250. 
Roscoe,  247. 
Rudorff,  309. 


Salathe,  325. 
Sandmeyer,  203. 
Sanford,  226. 
Schaer,  233. 
Scheibler,  71. 
Schilling,  271. 
Schnabel,  159. 
Schonbein,  162. 
Schrotter,  400. 
Sheffler,  378. 
Silbermann,  441. 
Sims,  239. 

Sonden,  145, 165,  362,  364. 
Soxhlet,  72,  200. 
Soyka,  219. 
Spring,  361. 
Stokes,  211,  292. 


Tacke,  149,  374. 
Tieftrunk,  273,  308. 
Tiemann,  10. 
Topler,  392. 
Travers,  9,  16. 
Treadwell,  211,  292. 
Troost,  194. 

V 

Vogel,  A.,  304. 
Vogel,  H.  W.,  211,  212,  214. 
Von  der  Pfordten,  154. 
von  Wagner,  246. 

W 

Wagner,  72,  200. 

Watts,  386. 

Weinhold,  99. 

Weyl,  163. 

White,  128. 

Wild,  163. 

Winkler,  C.,  22,  39,  108,  138,  139, 
141,  176,  181,  196,  202,  205,  210, 
230,  247,  287,  290,  326,  327. 

Winkler,  L.  W.,  145, 175. 

Wislicenus,  375. 

Wolf,  72,  200. 

Wolff,  218. 

Wolffhugel,  217,  225. 

Wurster,  162. 


YE   24010 


